Nobody has ever produced any reliable evidence that there is a population of large bipedal hominids other than humans living in western North America, and not for lack of trying. As far as I know, the best evidence is the famous blurry film of what may or may not be a human wearing a gorilla suit:

Now it seems to me that if sasquatches did exist, we should have found some evidence by now. Right? People have been all over the region where sasquatches are supposed to live, and they haven’t seen any. People have spent god only knows how much time deliberately searching for evidence of sasquatches, and they haven’t found any. Maybe we haven’t found any evidence because the things are especially stealthy, or maybe they can turn invisible, but a more plausible explanation is that they don’t exist. I wouldn’t say I believe sasquatches don’t exist, because it’s not about my belief. It’s just a fact that Sasquatches don’t exist.

On the other hand, extraterrestrial life. If life on other planets did exist, should we expect to find evidence? Well, if some tiny one-celled organisms evolved on some other planet than Earth, how could we find out? Well, we couldn’t, could we? Unless we sent a probe to the right planet with equipment to detect such organisms, and it happened to land near enough to detect them. But practically, any evidence of life on other planets is inaccessible to us. Does that mean we should remain agnostic about life on other planets? Well, for myself, I wouldn’t say that I believe extraterrestrial life does not exist, because of course I can’t know that. I would say that I do not believe that extraterrestrial life does exist. I neither believe nor disbelieve. (Of course, if I had sufficient evidence in the existence of extraterrestrial life, I still wouldn’t say I believe in it: I would say it’s a fact.) If you want to call that agnosticism then I guess you’d call me an agnostic.

A lot of people have trouble distinguishing between disbelief and lack of belief, and between believing something and understanding it’s a fact. I don’t believe in evolution, but I understand evolution is a fact. I don’t disbelieve that god exists, but I don’t believe that god exists. And if I had sufficient evidence of god’s existence, then I would say that god’s existence is a fact, not that I believe in god.