It only just occurred to me recently that all those people who have claimed to have been abducted by aliens then returned to Earth again are the ones the aliens didn’t want to keep. They are the fish that the aliens threw back for not meeting whatever standards they aliens have for keeping their catch.
Which may explain to some extent why so many of the survivors are seen as such unreliable sources. Whatever it is that impugns their character to the point that no one believes them when they say the were abducted by aliens might very well be part of the reason they were brought back in the first place.
Because there’s no reason not to believe that far more people are abducted by aliens than are returned after abduction. People go missing all the time, never to be seen or heard from again. If aliens are real, and they really abduct people, surely at least some of these forever missing are with them among the stars.
Plus, it makes no real sense for aliens to travel the almost unthinkable distances they have to to get here, just to pick someone up, poke and prod them for a few days, and then put them back.
Whether the aliens are collecting specimens to euthanize and pin up in a display on their wall, are trying to transplant select humans to some colony far away, or are picking up new animals for their pan-galactic zoo, it makes a lot more sense that they’re trying to find humans worth keeping, and that the returned didn’t live up to the whatever criteria they have.
And that would also explain the poking and prodding. They’re testing their catch for the qualities they’re seeking.
There’s a comic story here somewhere … two people get abducted, but only one makes the cut … the rejected one is offended and bitter … maybe trace their lives for a time afterward to see what comes of each of their fates …