I had an accident but don't remember it!?

A few years back I had an accident. I was walking on a catwalk attached to a piece of equipment I was working on. The catwalk sits about 8' above the ground. While working on the equipment something happened. One minute I was working the next I'm being taken to the hospital. I don't remember what happened or how it happened. My colleague was standing next to me and told me one minute I was right there and the next I was on the concrete below all mangled up twitching. I was told that a corner piece of the catwalk wasn’t secured correctly and I stepped back and fell. If it was something as small as falling why don’t I remember it? As hard as I’ve tried I don’t remember ANYTHING. I just remember working on the equipment then having an EMT asking me how many fingers I’m holding up.