Which gives a police officer the cause they need to search the car if they believe there has been a documentation of the accident and you do not come forth when questioned.

Beyond that if an investigative officer has been called to the scene of a car accident they do have the right to search all vehicles involved.

In fact they have several rights beyond that including towing your car to the police impound and doing what ever they need to it, in any accidents in which there were casualties it's standard procedure as the car will be checked mechanically by the police.