It happens to me sometimes, it's difficult to explain but when your GMOD loads up there will be an icon in your taskbar (if you can remember where it is before the game launches), if you click that area it takes you into the game.

It happens to me sometimes, it's difficult to explain but when your GMOD loads up there will be an icon in your taskbar (if you can remember where it is before the game launches), if you click that area it takes you into the game.