I think I may have seen similar when reconnecting monitors. It did indeed result in a pop out deciding that it was going to hide in a monitor location which no longer existed.
The monitor was physically there and connected but another monitor that I had used and my VR were not.
Despite the pop out never being used on those monitors Windows must have got confused and remapped something.
I basically needed to plug my smaller monitor into each gpu outlet until I found some desktop where stuff was hidden.