I had a very similar experience except I knew about the fall in question that caused it. Got bucked off into a water trough, back-down, and hit my neck on the side of it.

I have a vertebrae that is split vertically through the dorsal. It healed split open, such that the dorsal now forms a fork. The x-ray folks who found it were like uhmmmmmmmm so when did you break your neck?

Happened when I was like 13, didn’t know it broke, but apparently very lucky I didn’t die. But it’s the only bone I’ve ever broken so that’s fun and interesting!