This kind of situation is probably not that rare. I know a guy who got rear ended at a red light by a minivan while on his bike. Broke both of his legs. While he's howling in pain on the ground the woman who hit him gets out, stands over him for a second, gets back in the car, and drives away leaving him there to wait for other aid. She never got caught. He guessed that she got out to help, saw how badly she had maimed him, and decided to flee instead.