Pertaining to scientific evidence, I am aware of none, except perhaps through the work of people like Dr. Roger Leir, who claims to have removed artificial implants from patients. But again, said objects have not been designed with a technological finesse beyond the military's darkest capabilities. Moreover, if Dr. Leir thinks he has definite proof that the implants he has removed are without doubt non-terrestrial, then surelly he would publish his findings in peer-reviewed scientific journals, a Great Debate would ensue, and, if found accurate, Dr. Leir's findings would change the face of science, society, and government. Obviously, this has not happened.
Therefore I would suggest that researchers work their collective butts off to establish factualness, the single most important aspect of alien abduction: namely, its objective reality, whether Black Ops/hidden government or truly non-terrestrial contact. Minus proof of the phenomenon, all other talk is rather pointless, because it assumes abduction's reality - but assumes it without proof.