If they dont want to be seen, they will not be seen.

Even if they are seen, they can make sure nobody has memory of or or any evidence of them.

Im not presuming there are aliens, but one thing is for certain; if there are no aliens, then our evidence is correct. If there are aliens, they have been here all along and not necessarily on the actual planet.

Our notion of flesh-and-blood aliens flying around in little flimsey tin cans is retarded. If they are here, we cant even fathom their capabilities any more a person from 1800 can fathom the shit we take for granted today.