I've had a friend skydive out of a C150 from 4000 feet, while it was easy to open the door, it was extremely difficult to force it open far enough for the jumper to exit the aircraft. I therefore fail to see how someone could fall out accidentally.
I also trust that as this happened in the good old USA, Cessna will be sued as the Airplane Flight Manual does not have a section on departing the aircraft with or without a parachute.
Mutt.