Boiling water is hard to use. If you have the right type of aptasia peppermint shrimp will eat them. If you could post a pic or a pic that looks like it ill tell you if its the right type....
If the hole is "containable" try super glue gelling him into the rock. I've done that before with a little bit of success. Problem is they WILL find another hole to pop out of if there is nother one....