This may have happened to me. In my old place I put 3 of those floating type shelves up. Stayed up nicely for months.
Then one fell down knocking the other one down.
I paid a handyman to do it.
This is why I will never use those wall hangers for my guitars. I don't trust them.
I think what you are supposed to do is hold them back up, in their original position, with your hands expecting a miraculous indeed magic effect of them re-affixing themselves.
At this point you then wonder what the **** happened, and perhaps even suggesting fault with the screws / wall.