They definitely have it - the question comes up if it's out on the shelves or not. On the box itself that the cases would be packed in, it should have a date when they can stock it, which is supposed to be today.
I would politely correct the employee that it's the movie that comes out on October 4th. The free gift you get for pre-ordering the movie with a 7.50 deposit should be available today.
I would also let them know that they did the same thing with Snow White, UP, Beauty & the Beast....
And if they STILL don't believe you, have them check the back and read the information that's on the back of the case. It's clearly printed that the presell case should be available from September 4th until October 5th.