Deleted Property still exists?

Summary: In My Dragaera space, in the Book model, I initially created a field "Book Title". I later realized that I really just wanted to use "Name" for that, so deleted that Property. Sort of. If I click on "Book", it still lists "Book Title" as one of the Instance Properties. If I create a new instance of Book, it has a Book Title field. But when I try to Edit Book to get rid of it, "Book Title" is NOT listed in the Instance Properties.

The model got into this state weeks ago, so I don't know exactly what steps I followed. Very likely I deleted the Property from within the Edit Book view.