Motor shaft came through the endbell on CC 2200kv. Why?

I have a CC 2200kv motor that I run in my truggy. This past weekend while running it, I noticed that the pinion was sitting against the motor mount. Further investigation revealed that the motor shaft was sticking out of the endbell about 1/8th of an inch.

I've attached a photo, please ignore the dirt, I didn't clean up the truggy before I took the photo.

I'm curious to know what caused this to happen? Did the rotor slip on the motor shaft? Did a bushing fail?

I've got a repair order started with Castle, but not sure if they are going to repair/replace the motor because I don't have a copy of my receipt. I've only been in this hobby for less than a year and in the beginning didn't realize how it important it would be to keep receipts. I keep them all now, but of course this is one of the few I don't seem to have. I'm hoping maybe Patrick will see this and help me out.

ben