What'll really bake your noodle is the fact that we most likely couldn't tell if there was a pre-human civilization on earth, even around industrial levels. What we have now will easily last a thousand years - but not a thousand thousands years.

And my favorite hypothesis: Antarctica. If there ever was a species which flourished there, it's a lot harder for them to colonize the rest of the world than it is for us to visit Antarctica. Clothes you can just wear, and heating is pretty straightforward - but having to venture in a place where portable aircon failure means death will pretty much guarantee you don't build a lot far from home. Which puts a pretty high limit on how far a civilization could have gotten there and still have all traces hidden in the ice.