In this case, it means "busted."

In the packed school hallway, next to the teacher and various parents.

Her: "Mom, what's a nooner?"
Me: "Um...something that happens at noon."
Her: "So why'd you say 'thanks for the great nooner' to dad?"
Me: "Um..."
Her: Looking at adults, clearly wondering what's funny.
Me: "Uh... where did your backpack go?"

Wow. If you were going for maximum dose of humility, I am not sure you could have timed that better.  I will try to forget before you are fifteen and have a facebook page.