I read a question on here like six months back about some crazy theory, tell me what you think?

The difficult part is whether it could have happened. If it did, I don't think there'd be much chance of our knowing about it. However, the odds of encountering an alien culture capable of transplanting so many people and the odds of finding a planet close enough to earth that you could just drop Stone Age humans there and expect them to survive are both so low that I think this is science fiction.