Back when I worked at Airborne Express we'd hear about an ex-employee who had fallen asleep in either one of the aircraft bellies or a C container of freight.
Not sure how Fedex ships their freight, but our Naptimers had no way of getting close enough to bang on the cockpit door, unless they fell asleep in the Hazmat Container, because that was closest to the cockpit (So the crew could jettison it if need be).
Losing belly freight doors, because they weren't properly secured, seemed to be another one of our frequent stupid human tricks.