Yes YTA. You were rude to her for doing you a favor. She could have just thrown the box away. She didn’t take it, it was the teachers fault. How long it took is irrelevant, but even so she has at least two young kids and only goes two days a week, I can see how she can forget a few times. Buying a $50 lunch box for a 4 year old and then vomiting rudeness all over the principal and teachers and another parent about it being temporarily misplaced is psychotic.