I'm on the other side of this story, I can't for the life of me get my old magnets out. The old and look a bit grubby and need replacing. Tried the acetone trick. A good couple of whacks on the corner of a table. A super strong magnet to pull it out. None of the tricks posted on ecf work. These things have really taken root.
Heat it up with boiling water and then do the whacks - magnets loose their magnetism as it heats and regain again when it cools.