I'm sorry for your trauma and for the horse, glad that you are at least apparently OK.
About 15 years ago, I was injured in a fall, badly enough to need 3 days in the hospital. I did have a mild concussion (that was not what put me into the hospital), but witnesses tell me that I never appeared to be unconscious. I was talking to them as they tried to help me. As far as we can reconstruct, I have totally and permanently lost memory of about 15-20 minutes beginning just before the start of my fall. For a long time, I was afraid that I would suddenly remember it and wake up screaming or something. So far, none of that memory has returned. I am glad.
Do get yourself checked over by a physician, but don't worry too much about the lost memory.