'Shrooms are virtually impervious to screw-ups.
He'll find a Foot somewhere and someday he'll pop out all happy. If not, they'll roll around until they Foot.
If they're NOT where you'd Like them, slice off their stalk with a single-edge razor blade at their base, and "net" them to a rock with some "tulle" (pronounced: Tool) fabric and rubber bands or toothpicks.
But what you really should have in your tool-pouch, is a cheap Turkey baster from Target or Wally-World. That way, should you ever want to move loose critters around, or blow off the sand from your corals, just gently blow off with a focused stream of low-pressure water.
Plastic Basters are great for not only blowing softies out of areas they have (immediately) fallen into, but if you can get to the lose mushroom, you can suction them towards you by squeezing the ball of the baster, then releasing it after touching the; shroom.
I do it all the time.
Good question.