The worm will probably withdraw to a place in the rock that it cannot be seen or reached, just walking through the room is enough vibration for the worm to be scared, they are very sensitive.
Typicly they are detritivore/scavengers, but can pick at corals, or even hunt small fish at night when they get big. I have lost a scolly and a cynarina before I found one of these in the rock behind where they sat.