It appears as though demo discs, instead of the retail game discs, have been shipped out to numerous retailers incorrectly, according to Game Informer. Only Xbox 360 shipments appear to have been affected by the issue, and even then not all 360 shipments were part of the faulty batch, so there's still a chance you'll be able to go out and buy an actual copy today.
We've reached out to Warner Bros. for comment and will update with any further information we receive on the situation.
Update: Warner Bros. issued a statement to IGN saying it's recalling a "small number" of discs which, while labelled as demo discs, do in fact contain the retail game.
The statement reads:
"Warner Bros. Interactive Entertainment is recalling a small number of LEGO The Lord of the Rings video games that were released for the Xbox 360® video game and entertainment system from Microsoft to Walmart, Target and Toys 'R' Us in the United States with a disc labeling error. The discs in question are incorrectly labeled as demo discs, but those discs do contain the full game content and are fully functional. This error does not affect any other formats of the game. We are in the process of remanufacturing the discs and will get them to the stores as soon as possible. Consumers who purchased a copy of the Xbox 360 version of the game with the disc labeling error can contact customer support via email at email@example.com or phone at 410-568-3680 for a replacement disc."