[capt_noonie]

I'll bet you it's soaked down into the subfloor. When we took up our carpet to put in the laminate, we knew where Toto's favorite spots were. The backs of the carpets were soaked, into the padding, and even soaked into the subfloor, which you can't really replace. I mean you can, but it's a PITA. Luckily with the laminate it's much easier to clean up messes, and they are easy to spot, with a matte finish instead of shiny.

ETA: if it's the second floor, the subfloor is wood and very porous. If it's the first floor, most likely is concrete foundation under there without any wood. At least that's what we found when we did our floors. We still found some corners that he got the walls and then dripped down to the floor. So the concrete floor was easier to clean but not the walls. And this was a brand new house, so no previous dog smells.