If there is any flesh left on the skeleton, then there is a chance that the head will regrow. So, I'd leave it in there.

As to the question of which came first, the shrimp was most likely just doing a cleanup job. Did you accidentally come in contact with the bubble when you were moving it? My CC and trumpets tend to "fight" when the colonies get larger. My CC will send out sweeper tentacles that reach across to the trumpet, and I usually lose the head after just a short contact.