Receipted And Defeated

(My friends and I decide to do some grocery shopping together. The friend in question is in a relationship.)

Girl At The Register: “Do you want the receipt?”

Friend: “Only if you write your phone number on it.”

(The girl at the register starts to write her phone number on the receipt.)

Me: “Hey, [Friend], don’t you already have a girlfriend?”

(The girl at the register throws away the receipt, and my friend just glares at me.)