Replying to Plate Cracked In the Microwave

I got home from school today and I was microwaving a pot pie. I put it in for 12 minutes, and 6 minutes into it I hear a sound like plates clacking together. I opened up the microwave to find that the plate had split in half perfectly down the middle in a pretty much perfectly straight line, and it was insanely hot to the touch. I have never even heard of this happening before.

Has this happened to anyone else? I'm kind of scared to microwave on anything but paper now cause I have no idea what caused it.