Very glad you weren't hurt. I did have a good laugh though. I had a similar incident.

I had gotten a pressure cooker for the microwave as a gift. I do a brief glance at the directions. I think I made a pot roast. It was smelling awesome about 10 mins in and you could see steam and hear a small whistle. Which the directions had said would happen. About 5 mins later, the door of my microwave blew open along with a huge pop sound. the seal had blown and I had veggies all over the inside of my microwave.

I removed that weight that was the release valve, oddly it did not blow off. I took off the weight and was a bit mesmerised that half the lid had blown out the threading on the side.

What did I do wrong? I was supposed to have a 1 in clearance above the pressure valve. I didn't, I had about 1/8th of an inch. Rather than the pressure blowing the weight valve off since it didn't have room, the remaining pressure had to escape some how.

Pressure Cooker 1 Microwave 0
Pressure Cooker 1 My ego 0
Pressure 1 Cooker 0

The culprit