he couldn't have fallen out, although it seems for all intents and purposes as if he is about to be flung from the ride, notice the strap running between the legs of the woman on the left... I would assume this is also on the restraints of the boy and I doubt they would begin the ride unless it was secured on both and well, to fall out, he'd have to be cut in half
which would of course, have been more amusing than just plain falling out [;)]