Young Readers - MC loses his butt and can’t fart.

I just unlocked a memory and it was about a book I read in my youth about the MC losing his butt, and therefore unable to fart until he finds it. I think it was stolen.

I remember it didn’t have pictures, I remember some sort of villain who has collected the MCs butt, and some sort of airship… perhaps. It was somewhat comedic.

Did I dream this?