Logical thinking people:whom exactly are the " we ?"
Let me say that after the many thousands of "supposed"visitations as proposed by MR and his kind, that one would presume that some non Earthly artifact or physical implement would have by now been left behind: One would also logically presume that after these thousands of visitations, that they [the aliens] would make their visits official by now.
Again, yes, it's possible we may have been visited by Aliens or Interdimensionals, or time travellers, but as of now, we do not have convincing evidence to validate any conjecture.
They simply remain UFO's.