Closet 3B

So you've heard of kids writing on trees with little hearts around each other's initials signaling that they are yours and nobody else's? Ya, well we have that at my school. Just a little more harsh and more like, "Stay the heck away from him otherwise you will be punished." And it's not a tree. It's a bulletin board. Located in the south hallways their is an unused custodian closet 3B. And no one goes in until I unlock the closet at promptly 4 PM and lock it at 7. No one sees me do it, therefore no one knows it's me. So why is there a story about what happened with David and I... And more importantly, how do they know I have the key.