My Mushroom coral Disappeared?

This one local fish store that specializes in saltwater gave me a small mushroom coral to try out. I placed him where I wanted (he came with a small piece of rock he was attached to) and he did fine for about 4 days and then suddenly POOF gone! I checked everywhere for him! I even took all the live rock out of the way but he was gone. My peramiters were all perfect, so I don't know what happened. But about a week after that I had spotted some crabs hiding in the live rock. Within about a 2 week period I found them and removed them without damaging the rock (took out 3 little buggers) and also removed 3 medium sized bristle worms. There are other bristle worms though, I have seen them before but couldn't pull them out. Is it possible that the crabs or maybe bristle/fire worms killed and ate the mushroom coral? It has been about a month and a half since that had happened and was considering getting some start polyps today.