Lithics were, broadly speaking, more akin to how we treat plastics than metal tools. Lithic production results in enough waste that archaeologists give the waste a special name ("debitage") and even use it for destructive testing that would be unthinkable for more significant / less voluminous artifacts.
That leaves other evidence that's been looked for. Additionally, the Eurasian cultures that peopled the Americas are all known to have been heavy lithic users.
Somewhere, I have an old stone hand axe. It's really well-made. Not sure where it's from, but I believe it came from a European Stone Age dig, about fifty years ago (probably stolen. People weren't so circumspect, in those days).
