GENTLY pick up the tube and GENTLY squeeze it. You should be able to feel the worm inside. If not then dead duster and remove the tube. If you feel something inside (firm but soft) about 1-3 inches long then it is probably still alive and either dropped its head or when you moved the rock you may have torn the tube and it is trying to recover. Don't try to force it out. It is a filter feeder and strains things out of the water. If it dropped its head (the feathery part) it could be another 2 week before you see it come out. Then the feathers will be alot shorter. If you can feel the worm inside I would put it back and wait awhile longer then check it again in say about a week. Hope this helps
SiF