I've noticed occasionally that threads vanish, and wondered how it happens. Not mods, I guessed, because they lock threads and don't delete them.
For example there was a magazine salesman we recognised and had a go at. His thread suddenly vanished. Yet the previous thread run by his boss (now banned) remains intact.
I just tried on one of my own thread which had only three posts total. I deleted the first post and the thread vanished.
So a thread can be vanished but only by the OP.
Sorry if everyone already knew that.