I would personally say that you're just out of luck at this point. If the papers weren't in hand at the time of adoption than the kitten was either a) sold with a spay/neuter agreement, b) bought at a pet store, or c) the litter just may not have ever been registered and wasn't sold with any promise of papers. I'm sure there are 100's of little side reasons, but those are the top ones that come to mind.
Many breeders have a spay/neuter by date in the contract, and if you don't take on the responsibility to alter the cat and send proof to the breeder you void your rights to registration. Even though it would be the most responsible action as a breeder to make sure a kitten is altered, I know a lot of them will not hunt you down to find this out as there is little recourse that can be done (minus not giving you the registration). Almost seven years is way too long to find out what's going on, it's highly possible that the cattery doesn't even exist any more. I would just think of your kitty as a wonderful pet that just isn't registered, unless you're planning to breed - although seven years old is really late to start - then the registration won't mean much at this point anyways.
Question BengalBabe: Would it be easier for you to buy a few 3" binders and store all the registration papers, contracts, etc there? I run a photography studio and have paper work out the wazoo as well, but I rarely ever throw anything away. I have a big file cabnet and I'll keep current business things, current breeding cats, and recent litters in there. After it get full I sort things out and the important things that are signed, registration copies, tax forms, health information, and so on I'll save in binders that are labeled by the year. True I'll probably never have a need for most of it, but it's there if I ever do. But I'm the type that's always overly prepared to prove I'm right in court, so maybe it's just me.