****Update in post 22****
A couple of months ago, one of my cats peed on my stairs 3 times, which was totally out of the normal for her (I posted about it). So I took her into the vet and we found out she had bladder stones. Her urine PH was already pretty low, so the vet thought that her stones likely wouldn't be helped by the prescription food and that she would need surgery (or this other procedure called urohydropropulsion) but she suggested that since it wasn't life or death that we at least try the food for a month. We did that and low and behold, to everyone's surprise, the stones are now gone .
Which brings me to my current problem. I suspected that she was continuing to pee in that spot because it kept stinking even after I scrubbed, but I didn't have proof-- I never found it wet or caught her in the act anyway, and I wasn't sure if it was just the urine smell being hard to remove. But now I found it wet once, and I'm pretty sure she now just thinks this is an ok spot to pee. I am really not happy about it.
Any products for stopping cats from peeing that you recommend? If I were to replace my carpet, would she no longer do it because the smell would be gone, or do you think she's just focused on the place regardless of smell? I would hate to put new carpet in and have her pee on the new carpet! We do need to replace the carpet at some point, though I didn't want to do it right now. These stairs are the ones leading from our main level up to the upstairs where our bedrooms are. We have wood on the main level, and the carpet starts on the stairs and goes through all 3 bedrooms, so it's a sizable part of the house, but it does need to be replaced. I am afraid to do it though now!
The other thing I'm considering doing is getting another baby gate to put at the bottom of the stairs there and prevent her from going upstairs for a period of time, in the hopes that she forgets about that spot after a while and that I can get the smell out without her reoffending. They (I have 2 cats) don't need to go upstairs, as their litter box and food are down in our finished lower level, but they do spend a lot of time up there and they usually sleep with us every night, so I'm not sure if that will just piss her off more.