This is a problem with Occam's Razor that I've encountered before. The person making the claim, a claim which is unsubstantiated except for their own verbal testimony, will almost always opine that their subjective viewpoint is the "simpler explanation" than any that could be put forth by science. It's a difficult hurdle to overcome.
WGBH, the simple fact is that hallucination is known, studied, verified and documented by numerous studies in laboratory settings. (Kit and I have provided several links to articles describing these studies.) The circumstances of your experience are consistent with the descriptions of hypnagogic and/or hypnopompic hallucinations given in numerous medical and psychological textbooks, websites, and papers. Even if we remove the term "sleep paralysis" from the table (despite your description of feeling "frozen... stuck there"), the aforementioned hallucinatory phenomena remain as entirely reasonable, likely, and even probable explanations.
Bigfoot is not a known, studied, verified or documented organism in any laboratory or scientific paper, beyond the purely speculative. There is no type specimen and no independently corroborated account of its existence.
Therefore, the simplest explanation of your sighting, especially given the hunger, lack of sleep, nausea, collapse, isolation, novel environment, and feelings of panic and danger that accompanied the experience, is that you had either a hypnagogic or hypnopompic hallucination.
If you have some concrete reason why this is not the simplest explanation, I would very much like to read it.
