I've heard some people have directed a power head stream at the foot and basal area to get it to let go. A firm, but gentle stream, not anything that is going to cause damage. Good luck!
+1 on power head. just direct the flow towards its base and after a while it will either move or one side will come off a little, you can then grab and pill it off slowly.
I have been using the ice cube method for years on many bta's for a long time. Get an ice cube and all it takes is rubbing it on its foot and wallah....:splitspin....You have an unattached anemone.