I'm not sure if this has been mentioned in the last 10 pages but I've captured on shot of a backfire that dissapeared on a Zonda R. It was clearly a big backfire but it just moved forward (when taking the picture) into the car, but since the zonda is so low and the exhaust is fairly high up I could still see it on top of the car. It looked as if my Zonda R had caught fire above the motor.
So maybe some cars glitch out and move the image of the backfire into the vehicle (where it can't be seen usually) when photographed.