Unfortunately, I have developed the same problem in the living room as I did here, and for the same reason. Neighborhood cats wandering by, visits from racoons and opossums, all freak out a couple of my cats and they decide to mark their territory by peeing on the carpet in the window area. And once they do that the smell brings them back to do it again. And they aren't the only ones that are aware of that smell.
And now I'm committed to the rest of the upstairs because of course I can't just treat that corner and leave the rest. I figure I've got at least 600 sq ft left to go.
At least my boo boos are numbing up. The sanding has been tough with a painful hand.