So much of our views on the existence/non-existence of another bipedal hominid on this earth is shaded by our overall inability to grok that we are only just the victor in a very long war between similar species. This brutal natural selection process may have very likely driven the runner-ups into furtive seclusion. Given our propensity to visit murder on our own kind, this seems to be a sound adaptive strategy on their part. Say what you want on the kill/no-kill debate, you can't overlook the proof of humans' default setting of killing first, then examining what you've killed to learn more about it. We do that. A lot. We out-breed and out-kill all comers. We are the locust horde and we would sooner open a can of whoop-ass on you than spit. Every other sentient being on the planet knows that well, and a Sasquatch probably would know it better than anything out there.