How can we prove this? They could have had high technology and there would be no sign of it after all this time.
I think we would have found a satellite or some space junk still orbiting if the dinos could put one up. How about some platinum coinage too.
Humans junk would still be found 100 million years after we left earth if that were to happen. If nothing else, we should find unusual radiation where the dinos put radioactive waste dumps, even after 65 million years.