Ben Stein's Car Wreck -- Bueller ... Bueller ... Fender ... Bender ... (PHOTOS)

Ben Stein learned the hard way, even with a private driver ... you can end up in an ugly car accident.

We're told Stein was in the backseat of an EmpireCLS SUV in Bev Hills when someone in a Prius flung open their car door ... striking Stein's vehicle.

We're told cops didn't show up because it was so minor -- the drivers exchanged info and left.

Ben sat patiently and the driver took him to his destination. He's fine.

One thing's for sure ... Ben didn't look too impressed ... but does he ever?