I'll do what you ask (Patreon)

Prompto - Voluntary  captivity as a pleasure slave to protect your loved ones

Prompto negotiates the release of his friends..at a cost.

He agrees to go willingly and do whats asked of him. His captor has plenty of lucians but he doesnt have any niffs in his collection.

He doesnt realise who Noctis is so he's not really interested in the others anyway - but Prompto doesnt need to know that.

Noct and co. take a few days to find Prompto, by which time Prom has been groomed and probably drugged to keep him dopey

I don't imagine MUCH has happened but he still will take a while to feel better. The drugs they gave him means he doesnt remember a whole lot of what happened but it probably is still sitting in the back of his head ready and willing ot come out at night i his dreams.