I wanted to throw three Alien Carapace out of my inventory by dragging them out the top of the inventory window. I think I misclicked in some way and then the Alien Carapace followed my mouse while I could also control the camera with it. The Inventory and Character GUIs were gone. Unfortunately I couldn't take a screenshot of it because the left-click to take a screenshot wasn't registered. When I pressed escape to close the in-game screenshot feature the bug was gone and I could move the camera normally.