Well, if you own the game you should probably visit PSN and re-download it (to obtain your .rif-file).
If you don't own the game, you might try and look for a .rap-file (and use either PSNPatch or reActPSN) and "activate" the game.
If you can't find a .rap-file, you might find a "patched" .edat-file (or EBOOT), and then you need to replace that/those file(s) in the installed directory.