The following is reproduceable with Valve Index Controllers. Quickly alternating 'B' on the Index controllers causes the quick menu to quickly shift hands. After stopping, its possible to get a "phantom menu" (completely invisible) with the exception of the VRCat hanging off an invisible menu.

This bug doesn't appear to have any other issues or complications with the game and can be made to go away after one or two presses of 'B' on the Index controller.