Noticed it right away. Honestly, I thought it was a rag you were using for the books your were cataloging, to clean them or something. (I'm watching on my iPhone so I guess my vision isn't too clear on this thing!). Usually though, in a similar situation I don't want to embarrass the person by pointing whatever it is out (usually a skirt hiking up, static, something stuck to the person's clothes). I know it sounds crazy, because obviously I should help someone be embarrassed for less time by pointing it out sooner!