I’d never heard this story before; it is perfect:

On January 26, 2006, [Joaquin] Phoenix was in a car accident in Hollywood on a winding canyon road that flipped over his car. The crash reportedly was caused by brake failure. Shaken and confused, Phoenix heard a tapping on his window and a voice say, “Just relax.” Unable to see the man, Phoenix replied, “I’m fine. I am relaxed.” The man replied, “No, you’re not.” At this point, Phoenix saw that the man was famed, eccentric German film director Werner Herzog. After helping Phoenix out of the wreckage, Herzog phoned in an ambulance and vanished.

Whoever wrote this Wikipedia entry has done an excellent job because Werner Herzog does not just “walk away from the scene of the accident”, he “vanishes”.