Story Riddle

I don't know if this is old, I got it out of a riddle book and if no one has read it I'll have plenty more where that came from...

A man drives to work on a dangerous twisty mountainous road every day. One day, while at work, someone breaks into his car and robs him. On his ride home he suddenly goes off the road and plummets 5,230 feet to his death (obviously because he fell off the mountain). Why did a man so familiar with the road suddenly lose control? something was missing. It wasn't any part of the car, the mistake was human. What was missing?

-Jay