[Excaliber]

It's possible he was thrown out even with the belts on. If the belts aren't tight and properply placed an end over end might be enough to dislodge you anyway. Just a thought,,, I know when I'm racing I tighten the straps to the point of being uncomfortable, plus I run a five point, not the typical four point.

Something like a sudden breakage of an axle would cause the car to veer sharply to one side. A broken axle/CV joint would not be easy to see in the pics.