Does this make sense to you?!?

So in The Lion, The Witch, And the Wardrobe, when Lucy first goes into Narnia, she gives her handkerchief to Mr. Tumnus after he helps her escape. She says: "here, you need it more than I do". And then when Peter and Susan go into Narnia, and Mr. Beaver finds them, Mr. Beaver gives Lucy her handkerchief back. And then at the end after they become kings and queens, Mr. Tumnus gives Lucy her handkerchief. But it never said that she gave it back to him… so I was just wondering if there's an actual name for mistakes like this.