If you need the money you spent on a game back, it's doubtful that the store which has money is likely to be afraid of you in any way, meaning realistically, you're ****ed and should live with the fact you got scammed.
Perhaps learn from it and never actually buy anything ever again unless you have to (MMO's).
The store has a legal obligation to accept back faulty products (returns due to a change of mind are a different issue), specifically those which fail to meet the expected quality or purpose; not having the correct amount of CDs in the box equates to breach of contract.
