How Can You Remember If You Forgot?

I realized on Monday that I've been driving without my license since early December-- I needed to show my ID at the Philadelphia Zoo because I hadn't signed my credit card, but I couldn't find my license in my wallet-- but the funny thing is, I forgot that I didn't have my license by the end of the zoo visit, and so I drove home from Philly with no license and it wasn't until yesterday when Catherine reminded me that it was missing (she remembered at school and put her wedding ring on the opposite hand so she would remember to tell me to continue my search) and I found it in my little wallet, which I carry when I want to travel light, and the last time I used it was when we went to the city in December.