Venus could well have been habitable for long enough, yes! Models of climates of early Venus suggest it could have remained habitable to life on its surface until at least 715 million years ago. And it did have a global catastrophe. That was a global upheaval 200 million to 1 billion years ago when the entire surface was resurfaced. It probably happened because it didn’t have continental drift. One explanation of this is the “stagnant lid” hypothesis. Because it had no continental drift and the entire surface “turned over” over a period of a hundred million years or so.

We can tell the age very approximately by the numbers of craters and its entire surface is very new. It only has very big craters because smaller ones burn up in the atmosphere before hitting the surface. Those conclusions are based on an analysis of nearly 1000 craters.

If so, it might also have had a thinner atmosphere before that and the modern atmosphere could have been created during the upheaval. If so, it could have been a habitable planet until then, much like Earth.

But if so, there’s probably not much left of that original surface. After global resurfacing, heating of the surface to hundreds of degrees C (if it was habitable before), sulfuric acid rain and so on, I wouldn’t expect footprints or any structures to survive. There might not be much at all left from that early surface.

We could have meteorites from it on our Moon however. But - how likely is it that a meteorite from Venus carries evidence of technology? It could have evidence of biology though. We could even find pristine organics from Venus and perhaps even entire small multicellular creatures if they existed.

Annabel Cartwright in her "Venus Hypothesis" goes so far as to suggest that large impacts on Venus combined with the global resurfacing event could have sent material all the way to Earth as recently as the Cambrian and Ordovician periods. She thinks that this might have been a time when it would be particularly easy for life to be transferred from Venus to Earth. Not directly through volcanic action but through large meteorites hitting Venus during the resurfacing event, while it still had a relatively thin atmosphere.

She suggests that the increasing day length on Venus would have given an evolutionary advantage to life capable of extended deep hibernation states, high resistance to extreme temperatures and radiation. She cites examples of early life with these capabilities such as the tardigrades, nematodes and Triops cancriformis.

Tardigrade (water bear) drying out and rehydrating. While dried out it is one of the hardiest of all multicellular lifeforms,, able to survive even the vacuum of space, extreme cold and heat, and quite high levels of ionizing radiation, a thousand times the levels that are fatal for humans. It can survive in the dormant state for at least a decade and is the top candidate for multicellular life that could be transferred on a meteorite.

What about shock of ejection from a planet? Small things less than 100 microns across can survive, but in tests of impacts on a planet or the Moon, plant seeds break apart (for instance). So what about Tardigrades? They are complex multicellular creatues with around 40,000 cells. It turns out that resisting impact shock is another of their many talents! They survive impacts of 3.23 km / sec, the highest speeds tested in the experiment with shock pressures up to 7.548 GPa. After rehydration there were some tardigrades still swmming around :). Here is another experiment where they survive impacts of up to 5.49 km / sec. They can also survive accelerations of 16,000 g for one minute, in another experiment (this is different from an asteroid impact scenario though which involves accelerations up to tens of thousands of gs in 30 ms).

So they might be pre-adapted to survive passage on a meteorite from Venus to Earth. Also life might have evolved more rapidly on Venus because of the higher levels of radiation there. She suggests this as a possible explanation for the species that arose during the Cambrian explosion with apparently no predecessors and only surviving for a short period of time on geological timescales. She also makes an interesting point that early Earth had connected seas, but early Venus might have had disconnected seas so permitting different forms of life to evolve in each one, so it might have had a lot more genetic diversity in its seas than Earth had, similarly to the way isolated islands on Earth have divergent populations of land animals. If her hypothesis was right, then we'd expect to find those meteorites from Venus on our Moon, from time periods on Venus as recent as the Cambrian explosion and the Ordovician period. And then could compare those with meteorites from Earth at the same time.

It’s a rather way out hypothesis perhaps. But we could be “Venusians” :). Others think we could have originated from Mars as single cell life that got to Earth much earlier on over three billion years ago when the solar system was more habitable. Some also think life could have got here from Ceres.

Another thing to bear in mind - intelligence doesn’t equate to technology. Imagine if you had a civilization of parrots - the grey parrot is amongst our most intelligent non human species. Even if they developed speech, writing, simple technology, it would be pretty hard for them to do much. And if fish or octopuses - or quadrupeds like goats or whatever were actually as intelligent as us in the past, any of them, then we wouldn’t get any evidence at all as they just don’t have the physique to do tool using. Or live in the sea so can’t make fire easily.

I think that actually the chance of an intelligence developing technology may be quite low. Which leads to an interesting question - are we really the first species as intelligent as us on our own planet? Or only the first ones with technology? I have no idea how you could decide if some past species known only from fossils was intelligent in the sense we are. You can’t tell by the brain size as after all grey parrots have very small brains, maybe large compared with their body - but would you guess that grey parrots are amongst the most intelligent of all species apart from human if you just had fossils?

Alex (gray parrot) - showed perhaps the most advanced understanding of language of any of the creatures tested to date.

So, it’s going to be pretty hard to rule out intelligence. But you could make a dramatic discovery of intelligence through technology. But I’m not sure how that could happen with Venus unless they developed space technology and we find their artefacts somewhere in space. However if they did, it can’t have lasted for long, as there isn’t any sign of any being doing extensive space exploration. We’d surely spot their tracks on the Moon or Mars if they had. Well - unless they also had a strict policy of not interfering… So that they have minimal traces somewhere, a few asteroids they mined maybe, but they never landed on any Moon or major planet or only studied them carefully remotely.

Anyway - that’s rather “way out”. However if they did develop technology - well - space technology is only a few thousand years after the origins of simple writing and the most basic of modern tools. If they got to the point where they made recognizable buildings - well - I’d expect they probably also got as far as space technology and so we might find traces of them in space somewhere. If not though, if non technological intelligences, I think hard enough to discover them on Earth, surely impossible. But we might find evidence of multicelular life in Venus meteorites in the ice in the poles of our Moon.