One of the ways that we figured out continental drift was that you could figure out how species got from A to B, and how they evolved afterwards.
Any scientist studying the fossil records would find it dead obvious that there was a period when a lot of species managed amazing migrations.
Even without a single fossil of us, or any geologic record of our presence (which we've left plenty of, incidentally), that would be a giveaway that something interesting happened.
Cheers,
Ben