The carpet was upside down so the rubber side was up, but when I was returning my car from the vet he peed and some got on the rubber. Is there a way to get the smell out without buying a new mat?
Try Nature's Miracle. Let it soak in. Sometimes the only thing you can do is to replace the carpet. (Once moved into a house where we had to replace carpet, pad and seal the subfloor to get the pee smell out!)
I've never found anything that will destroy cat pee. Spend time on it if you want but be prepared to replace the mat. Then, buy a cat carrier and a big shallow plastic bin for the carrier to sit in (an under-the-bed storage box works well, and is generally convenient for carrying any potentially messy items).
Try soaking and sponging it to get rid of as much as you can, then liberally spread bicarbonate soda over the area. You leave the bicarb on it for a few days and then just vacuum it up.