Sorry to hear it. It seems as though Mafia II has been removed from the marketplace as a sale item. You may be able to get it from your download history though. On the console go to Settings>Accounts>Download History and search for the item.
If it will not download from there though that means that it has been removed from the servers entirely.
Did this solve your problem?
Sorry this didn't help.
Great! Thanks for marking this as the answer.
How satisfied are you with this reply?
Thanks for your feedback, it helps us improve the site.