Not really surprising. Carfax are notoriously error prone.
Two years ago, my BMW 325i collided with a deer (the dear ran into the side of the car). $3500 in damage was repaired by insurance. When I sold the car over the holidays, no mention of the repair in the Carfax. Of course, I did disclose the repair to all of the interested parties and the ultimate buyer.
Here is what Consumer Reports found:
Consumer Reports - Don't Rely on Car History Reports