Harry Potter: The "old discoloured tiara" that is missing from the Half-Blood Prince movie...?

Alright. So in the most recent Harry Potter movie, Harry Potter and the Half-Blood Prince, there's this scene in the Room of Requirement between Ginny and Harry that is not in the book. Ginny helps Harry hide the Half-Blood Prince's book (Advanced Potion Making) because the spell Harry used, sectumsempra, almost killed Draco. And then that random kiss happens. Anyways, in the book, Harry hides the Half-Blood Prince's book because Snape wants to see it. He does this alone, not with Ginny, and he intends to come back and retrieve the book later on. He uses a bust and an "old discoloured tiara" to mark the place where he hid it. This is important, because in the seventh book, that tiara is revealed to be a horcrux, Rowena Ravenclaw's Diadem, which Voldemort hid in the castle when he went to apply for a job there as Professor of Defense Against the Dark Arts. Harry remembers the tiara when he is searching for the horcruxes, and realizes what it is. It is missing from the movie. Or at least I think so. Maybe it was in the background or something? If it really is missing, how are the filmmakers going to get around this problem in the next movie?