If a beast that big undergoes any kind of accident, or just has a sudden heart attack, you'd see at the least a skeleton in the wild. Birds, beasties, bugs will eat the flesh, but the bones persist until buried and demineralized (and even that leaves a fossil). Supposed Sasquatch territory should be searched for such skeletons.
I spend lots of time in the woods of the Pacific NW. Haven’t seen a Bigfoot - but have never seen a skeleton of anything either. I’m guessing probably due to the thick brush. But perhaps also the bugs, soils, critters as well. In Eastern Washington state where it is dry you see LOTS of skeletons of stuff.
Bones don’t last long in the wild. Kill a deer and come back in six months and you will see what I mean. I agree much mor research needs to be done.