I am experiencing problems with icons added from a plug in, especially Iconify. Often after placing the Icon on a frame, the icon “disappears”. It is not visible on the frame nor in the layers but I can see it in the Figma mirroring app. So i know it is there but it is not visible, so I can’t delete it either.
The only way I have discovered to fix this, is to restart Figma, which is not great.
Select the frame that has the problem then hit delete, then after that click “CTRL+Z”.
It worked for me this way, I hope it does for you. Have a nice day.