paper or plastic?

So, I went to Half-Price Books on my lunch break to pick up a quick, trashy read. It was a rainy day and I figured the book + my couch after work = good day. I found a book that fit the bill and went to check out. The cashier went to put my book in a bag and the conversation went like this:

Me: Oh, I don't need a bag
Cashier: Are you sure? It's raining.
Me: Nah, my hair is already a disaster.
Cashier: [silence]

My hair is already a disaster??

I stood there awkwardly and played back the conversation in my head, realizing he intended the bag to protect my new used book. Why, WHY, was I thinking about my hair like some old woman, freshly coifed from the beauty parlor?