My kid knows me too well

The kids and I were in the living room when I thought of a book I needed to return to the library.  I wanted to get it from the bedroom before I forgot, so I took off running down the hall (my memory is THAT short-term anymore).  From the living room, I heard Sarah ask Noah, "Why did Mom just go running out?" and Noah answered in a bored voice, "Oh, she probably just started her period.  Don't worry about it."