List of aliens left behind: Apache Death Cave Aswang, Moth man, Bigfoot, The Rake, The Flat woods Monster. Many people say Bigfoot is just a missing link. But a girl lived with some Bigfoot. They speak Telepathically. How do you explain that. The Flat woods Monster is similar to Reptilian.
I do believe there are aliens. I think given our current knowledge of the Universe it is hard to deny that it would be easy for other Earth-like planets to exist. I do not believe life is so rare that other planets would not contain life and more than likely other humanoid life forms.
This is a vast cosmos, so vast that it would be arrogant to be so earth centered that we do not realize the possibility of life in many other places. However, these other places are at such a distance that they may not even exist in the same dimension as we do.