It seems certain shipments of Lego Lord of the Rings for Xbox 360 have had some mix-ups. Users are reporting that instead of the full game, the new, sealed boxes contain demo discs meant for video game dealers to run in their stores. It would be a good idea to check your copy before leaving the store, since wasting gas is not covered in your replacement trip.
It's not the first mix-up reported about games receiving different discs. Earlier, Black Ops 2 for PC was reporting that the second disc in the box contained Mass Effect 2. I'm not sure what's going on at the manufacturing line, but I'm gonna blame Steve. Dammit Steve! You had one job to do!