I had a similar situation with my previous car. I was involved in a minor 2mph accident and the other driver insisted on calling the cops. Neither car had any damage and no insurance companies were called. When I went to sell the car I found out that the carfax showed an "Accident" with "No Damage Reported To Carfax" on the report.
All of those reports are a crock!
I bought my current 2010 335i with a clean carfax. However on the autocheck report is shows that the auction house reported damage. I had the car checked out prior to purchase and there is absolutely nothing wrong with the car. I later find out that the auction reports damage to autocheck to cover their ass in the rare event the purchaser finds something wrong and it was not reported.
It's all a bunch of BS. Just get the car checked out before buying it and if you do decide to buy make sure you get at least a 15% discount.