You know, thinking on this, think of how hard it was to find various outlaws and renegade mountain men? Even in this modern age of drones, helicopters, heat-seeking sensors, etc. Remember that guy robbing cabins that was on the run in the mountains for quite sometime despite all the police forces looking for him? Or that anti-abortion bomber and Olympic bomber? Or those freaks who kidnapped that Olympic skier to get his son a "mountain bride?" And all the drug-growers, moonshiners, methlabs, etc that elude capture in state parks and wilderness areas? So...if Bigfeet are humanoid and so maybe has some smarts in addition to animal instincts he hides when all the hunters or people are around or even has hidden shelters they have constructed? Or they help/warn each other of the comings-and-goings of the humans?