Disagree with Bogie, thought it was a good post, and a maybe we could learn from it.
Had a similar thing happen to me with a Walther P99 in a Sidearmor holster with the J-hooks, I believe they are called. Getting out of my car to buy a newspaper in a stand it popped out and skidded across the road a few feet (not into traffic), scratching up the slide. A driver may have seen it, it was not a busy road, although I scooped it up quickly.
I think I somehow unhooked the J-hooks, were just kydex half loops that hooked on your belt, while bending and twisting to get out of the car and then managed to pop the holster, which was fairly large for a full sized pistol like the P99, out.
Based on that I now prefer a more secure method of hooking the holster to the belt, like a fixed full loop or a snap on full loop at least. Your clip looks more secure than my J-hooks but I will still be uncomfortable with it.