I would take the entire piece and put it into a small clean tupperware with no top, inside put another small rock. When it detaches remove the original piece and let the mushroom move around until it attaches itself to the small rock. The tupperware prevents direct flow from blowin it away and just having one rock in there ensures it will attach and be strong enough to move into the main display flow. Read about this method on some forum, cant remember exactly where
-Dave