In my time I've come across, dead raccoons, dogs, deer, and several birds while hiking around in various parts of the country. I've seen plenty of sign and scat of mountain lions, bobcats, moose, elk, bear, etc. I've seen all but mountain lions alive as well. Hell, I've caught a soft-shelled turtle with my hands in the Pecos River and rare frogs in the Colorado Rockies at 10,500 ft. If you are arguing that no one should have found a dead sasquatch, let alone shot one, that argument is pretty silly. North America isn't the Congo or the Amazon. There are 300 million people kicking around and as a whole is intersected with roads, has planes and helicopters flying over, etc. I've been to some lonely places, and I tend to find MORE animal signs and see more of them too, not less, the further I get away from all that.
I don't know how adults can believe in this sort of thing.