Other sources mention that the note had tape on it (which TSA does not use in notes) and was in poor condition. TSA labeled it as screened and cleared, indicating there was no need to open it. It is possible that someone else destroyed it and put an old notice inside. I've heard quite a few stories of broken instruments during air travel, but typically musicians blame the airline (e.g. https://youtu.be/Th0qY3d6oHA)