I’ll expand on that - it would take a significant number of them to sustain a viable population, and not just ten or twelve or twenty. There’s much less acreage of deep, inacessible wilderness than there was even fifty years ago and it’s not contiguous. They’d have to have developed a tribal social structure like many primates do, and I’d expect a means of interacting with other tribes some distance away. That would mean traversing areas where humans dwell, exposing themselves. Someone would have produced conclusive evidence of their existence by now, even if by accident.
Have you ever been to Northern California or the Pacific northwest? Millions of square miles of wilderness and forests with hardly a trail or two lane road through them.