If we assume Bigfoot exists and is intelligent, I would suggest they are more like an indigenous tribe or people like those un-contacted tribes in the Amazon rain forest or the folks on North Sentinel island.
Kind of left alone to manage and govern themselves.
It kind of depends how far away they go. There is this concept called a "light cone" and it's basically the information that could possibly reach you as you go through space/time. If they land inside your light cone, they could possibly reach earth with a signal. It may take a long time and they are long gone, but it could be possible.
If they are outside the Earth's light cone, there is no possible way for their signal to reach earth.
https://en.wikipedia.org/wiki/Light_cone