Call me cheap...

I received a call from a mom that I volunteer with at Kylie's school. She said when she was working with the kids in the class the other day, the kiddos were sending out letters to themselves and when she was helping Ky put the stamp on the letter, she said Ky got very serious and said, "are you sure we can use these stamps? These are not toys or stickers ya know." The mom assured her it was o.k, but Ky proceeded to protest. She finally convinced her she had permission and if you are in fact mailing something, you can use the stamps. Can I just say in my defense, nothing is more irritating than when you need a stamp and then find out they have all been used on a self proclaimed work of art by a kindergartner. Can you tell we've been down this road before? I don't know whether I should be embarrased I got caught being so cheap or proud that she actually listens to me?