I had a similar experience, when a friend got hit by a car and hit his head when falling. After all due checks were performed at the hospital and I was allowed to see him, his memory would reset every five minutes. He would stare blankly at the wall for a few seconds, then ask the same questions all over again: where am I, what day is it, and so on. After a while we just gave him a piece of paper with a brief explanation of what happened and some FAQs. I must confess, I had some (innocent) fun.

Now he's fine, as if nothing happened, and we laugh every time we remember this.