In the movie, unlike the book, Harry and Dumbledore Disapparate from the Astronomy Tower. "Being me has its privileges," Dumbledore said. When they returned from the cave and Draco disarmed Dumbledore of his wand, Dumbledore didn't Apparate.

Could there be any chance that you have to have your wand to Apparate/Disapparate, or was there anything else preventing Dumbledore from Disapparating? Rowling must have approved this for it to occur in the movie.