Once is happenstance. Twice is coincidence. Three times is enemy action. Four times is Official GNOME Policy.
- Press the 'Menu' key on the keyboard
- Press 'Esc'
- Focus is now beneath the screen locker
- Press Alt+F2
- Start 'gnome-terminal'
And here's another variant of it from August, which is possibly even easier: "Holding menu key causes window flood and desktop freeze." This probably means "hold down the Menu or Super key and wait for gnome-screensaver to run out of memory and crash, unlocking the screen."