Y'know one thing that REALLY always burned my arse when I worked for any parts store? Warranty info. (Sorry, this kinda applies to the original poster.)
NOBODY keeps their friggin' receipts, it seems. I guess I grew up in a totally different time, country, world, dimension, or whatever. As far back as I remember, the case was always, "No receipt, no return." Ever since Sam Walton and his evil empire came along and screwed over the way retail businesses are run, suddenly NOBODY feels they are responsible for keeping their receipts for ANYTHING. Is it really so hard a thing to do? Take a standard mail envelope and tuck all your receipts in there, and chuck it into a file cabinet or something at home (NOT in your glovebox, because heat kills the ink/paper). Is that REALLY too much to ask? Apparently so.
Soooooo, some auto parts company execs got together and said, "Hey, we can get around this problem if we just take their info down and log all their warranty purchases in one big database." Cool idea in concept, because (in theory) you can not only look up warranties in customers' histories at that store by name, phone number, ZIP code, etc. but also you can check to see if OTHER stores have their stuff on file. Neat, huh? Here's where the system fails, due to general human stupidity/laziness:
1. Again, NOBODY keeps their receipts. Thus, nobody remembers what damned store it was where they bought their part(s).
2. Cell phones. I FRIGGIN' HATE CELL PHONES. Why? Because so many of these technophile douchebags that just GOTTA have the latest and greatest phone will change their phone number TEN TIMES in 2 years, so they can NEVER remember what phone number they had their warranty listed under.
3. "Well, it's my relative's car, and they had some shadetree mechanic guy put it on, and he bought the part with his commercial account, etc." so nobody has a damned clue who even bought the part, thus there's no way to know WHO to look for the part under.
4. Paranoid conspiracy theorists. I can understand not wanting to have personal-personal info listed in there like a Social Security Number or anything, but good lawd ... all these people ask for is a NAME, a PHONE NUMBER, and a ZIP CODE. They don't even need a freakin' address, just those three basic, relatively anonymous identifiers. And I had SOOOOOO many jackholes throw a total hissy about it ... and then throw ANOTHER hissy fit later on when they can't remember what fake name/number they insisted on having the parts dude enter into the system, so they can't retrieve their warranty info.
5. Idiot employees. Yes, this is a factor, but only about 1/5 of the time. (If it weren't for the above 4 items, this wouldn't even be an issue, anyway). As with the OP's case, I've had stupid employees enter my warranty info under totally unrelated vehicles. I ALWAYS have my receipts, I know what number/name my stuff is under, but when they go a step further and try to look under what vehicle it's listed with, I find all sorts of totally random BS ... Mustang parts listed under Chryslers, Hondas, and so forth. If I have two legit cars that I own listed in their system, they'll put parts from one under the other, and sometimes (like when I had a 'Stang and a Town Car) the parts interchange between the two, so it's tough to tell which one was for which car.
6. System file deletion. Again, I ALWAYS keep my receipts (because I know what a PITA not having them on hand can be when you're on the other end of the counter), but what REALLY chaps my arse is every once in awhile, some yahoo in their network randomly deletes entire vehicle history info out for no good reason. I'll have a receipt in hand and all, and even the dude working there is familiar enough with me that he remembers me buying the part, but suddenly the crap just isn't there in the system, period. I've even had some places try to refuse an exchange/return even when I had a receipt in hand, trying to say I already refunded the part previously and that's why my stuff's gone. (At which point I have to become one of "those" customers that pitches a fit and demands upper-management, but that's only because they're the only ones that can technically override the system and force a transaction.)
7. Warranties are NOT TRANSFERRABLE. Simple concept. If YOU didn't pay for the part, YOU don't get the warranty. Works the same way with dealerships and any other kind of warranty elsewhere, so why expect different with car parts?
I know, I know. This is America. Nobody is reponsible for their own actions. Everything is everyone else's fault. And, by this idiotic rhetoric, people expect auto parts companies to be fully responsible for keeping track of everyone's frickin' receipts. Sorry, but it's logistically IMPOSSIBLE for a company to keep track of everyone's warranty info FOR THEM. This is why they give you a receipt when you buy things - so YOU have that information in hand, and it is YOUR responsibility to keep track of YOUR warranty info. Again, put your receipts in an envelope and keep them somewhere that they won't get discarded or destroyed. Simple, easy, doesn't cost a thing (hell, you could use an old junk mail envelop, even), and saves EVERYONE a lot of hassle.
If this is too much to ask, then by all means, stop buying your own parts and let a shop do all of your repairs (and charge you labor AND a marked-up price on the parts), because they MUST keep all of their purchase history on-hand for their commercial accounts.