Board Thread:Character Discussion/@comment-3407907-20140929025217/@comment-24674051-20140929140055

the hat that Rumple found is none other than Yen Sid's hat from the Sorcerer's Apprentice. If the appearance of the hat wasn't enough, the backgound music for that scene also incorporates the main theme from the Sorcerers Apprentice.

Now, as to whether Yen Sid is the author of the book, I don't have a clue, but I don't think so, personally.