if there is a known loose article in the cockpit, then turning the aircraft upside down is perhaps not the best way to proceed?
It was SOP (well it was when I was in the mob) that if you thought you may have a loose article and after ripping the a/c to bits you still couldn't find it, you got the jock to invert the a/c on the next sortie to see if it fell on his bonce.
Obviously this only applied to fighter types...