Mushrooms, do not adhere well with super glue. There base is living tissue, and they shed the outer layer like we shed skin cells.

There are two ways I have heard to attach mushrooms:

1 Use lace to tie the shroom to the rock where you want it, then give it time to grab hold.

2 use a plastic toothpick to spear the shroom, and a hole in the rock, and wait for the foot to grab hold.

Robert