User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-24017367-20131006185024/@comment-7742465-20131006221918

He's saying that the Yankees cap stopped working after Annabeth argued with her mother. She can't turn invisible anymore. However, that hat Annabeth is wearing in the character art is just a regular hat. It doesn't have a Yankees logo on it.