Pet pee on rug? I am in town at ym parents house, and they own had...

I am in town at ym parents house, and they own had a problem near a pet, I think a cat have been urinating on the rug. They cant find the exact location and it doesnt other smel.. they have tried plentiful different things, like shampooing the rug, Resolve, a bunch of hearth rug cleaners and still the smell persists. What can be done more or less it, any home remedies or something. My parents are really wanting to avoid buying a new rug considering this one is one and only a year old. Please any counsel would be greatly appreciated. Thanks
Difference between Roomba 550 and 560?
Answers:    try using white vinegar it neutralises the odour and kills it. its worked on adjectives my carpets and i have 3 cats!! its smell pretty bad at first but once its dried the smell disappears, and its a amazingly good opening of getting rid of the stench of cat wee however long its been at hand! hope this helps its worth a try....
SNEAKER REMEDy??
Go to the pet store, and buy a bottle of "Nature's Miracle". Spray it everywhere. It eliminate the odor of the urine so the cat won't smell it and pee there again.