Hi RVman
The prop falling off does not mean an automatic crash. If the prop had a weighted prop nut things would be more interesting. One of out fellows had the 60 size engine fall off the plane. While he had much experienced, it was thought he would not make it, and he clearly yelled for help. He had good altitude. One of our old timers ran over (hobbled over as best he could) and he talked him into a safe landing. Keeping the pilot calm was the main thing. Had to come in and hold a LOT of down elevator, modulating it carefully as needed. A perfect landing. The engine was found and was not damaged.