That looks very small. Was it an actual blow out or just a puncture? Blow out means all the air come out at once and car will lose control for a while needing you to rein it in. At least this is my understanding.

If you felt like you hit a pothole and then realized no air means you probably did hit a pothole?

No offense but just trying to understand what happened.

Anyway, just sharing my experience, I have had many such incidents with the side walls being torn or blown but usually as a result of brushing the kerb or touching something. Never in the middle of the highway. One thing that I just realized (saw it in a post) was that all the tyres were contis. 2 each on 2 different E200s, 1 fiesta & 1 cerato. Never happened on other brands even cheaper ones. While these tyres were very good & grippy so gave a lot of confidence to the driver, but they get damaged very easily. I really hate it when I lose a good new tyre. I will probably pay more attention to the sidewalls of tyres in the future.

Good observation! And the slits do look like pothole damage.