Six months ago, I had a similar crash. I was riding alone and stupidly, had no i.d. on me. I was just taking a spin in the neighborhood. I have no idea what happened; I woke up in a hospital bed. My best guess is I swerved to avoid a car and tumbled. I had a gash on my forehead and I was seeing double. I damaged the fourth cranial nerve and had to wear prism glasses until just a couple of weeks ago. Fortunately, my eyesight straightened out without surgery.
My bike is fine; the police took it back to the station.
I have been back on the tandem, but I have to admit, I have not been back on my single yet. I will get up the nerve, and I hope soon, but I assure you, I will not ride alone again.