Hey Daravon! I'm afraid your prisoner is gone forever. Why that would happen is a bit long to explain (this seems familiar
):
1) When you have someone in the process of brainwashing, and someone releases them, they go straight back to their owner. That is, it's
not as if the guy who released them, in turn, captures them and puts them in their own toilet; rather, it's as if they freed them, and they go back to their
original owner. Therefore, you never get an option to get them back.
2) Particularly, the dude you capture during the tutorial is a special case, as it's generated by the game for just that purpose. That is, it doesn't
have an owner to go back to; if they are freed, they simply evaporate forever.
That said, you were lucky, I had my own dude released within hours of completing that tutorial.
I don't think you get much from actually converting someone aside from the SPLithium drip during the process, so you did't lose much.