Been trying to ID this worm on the side of a rescue coral. It is a hard shell with the mouth on the left side. I think the coral is a torch, but still recovering. The coral has white milky stuff coming off every few days.
That does look like a very large vermetid snail, yeah. They send out mucus nets to snag food and tend to irritate corals in the process. Big ones don't multiply and run amok like the common little species does, but you should probably still remove this one, sadly.