The book that came against her head caused a form of amnesia which even Twilight couldn't have been able to figure out. As icing on the cake was every single bit that had to do with the vampiric kind of ponies and Rarity from an hour before she was bitten until she woke up behind the boutique, just gone. It was unexplainable to her just how it happened and she was too stubborn to just go up to the building and ask what happened to her. Pride was something that stood high on Trixie's moral list and there was a joke that she should have been born as a pegasus in Cloudsdale.