Is it normal can't remember where i got a certain injury?

I'm not talking about the small scratches you may sometimes wake up with. I once had a deep cut over my shoulder, and as a result avoided showering for several days (but still did my best to maintain hygiene otherwise, like washing my armpits and change clothes), because I didn't want to get the water stream and even less soap into the wound. But the strange thing is I cannot longer remember how I even got the injury in the first place, and dont see any logical explanation. I think I did remember it for a while. And to be clear I have healed from the injury long ago, I just came to think about it.