Thanks for your good-will, and doesnt' it just frost ya when your good deed is "not returned." anyway, on the cat's behalf, it was probably scared witless, and if there wasn't a way for there to be a cat box, it could very well have just peed. Spraying is marking territory and done as a warning "this is mine! Stay out" usually by unneutered male cats. Just fyi.
Now to the problem. There are a number of things to use, but without knowing where it is--well, not all solutions work for the same problem.
Steam cleaning will take the smell out. Some people swear by Zero Odor especially for use on fabric-but it's expensive and can only be gotten on the 'net. Just put Zero Odor in your browser. If it's on plastic, you can use 1/2 alcohol and 1/2 water and wipe it clean. There are multiple other items that can be used to deodorize that you can purchase and all make claims. One that is very good is an enzymatic cleaner that you can find in PetsMart, etc...called Nature's Miracle. It will take few days to take the smell out, but can be used (I think!) on all types of fabrics, etc.