I’m afraid the chances of him being real and us having never seen him before are pretty low. Especially in this world with so many people around. But, there are still many regions of Russia, South America and Central Africa which haven’t really been explored so he could still be lurking in there somewhere.
Nobody really knows what happened to Neanderthals (our closest extinct ancestor) so big foot could be one of those, still hiding from us! Doubtful, but possible! You should become an scientist and find out!