Save me from the urine smell!

Hope someone can give me advice on getting rid of a persistent urine smell, as I'm about ready to pay someone a gillion dollars to rip up a perfectly good hardwood floor!

About a year and a half ago the toilet in one of our bathrooms got stopped up and possibly overflowed a bit. (Yes, I know, you'd think I'd know if it did or didn't, but I wasn't home and the guilty party isn't 'fessing up). The toilet stayed plugged and full a few days until adults were home to deal with it. We unplugged it, and I cleaned it and the surrounding areas and hardwood floor thoroughly with bleach. In my memory, this is when the urine smell started, though I could be wrong, as its been going on so long.

After the smell started, every week or so I'd go in and rescrub the whole area. At one point, I even got a flashlight and got down on the floor, checking every visible surface of the toilet. I also sprayed the animal urine enzyme odor remover stuff. I have young males in the household, as well as an elderly cat who was sleeping in that bathroom, so I assumed that was the problem and just kept cleaning and cleaning. Cat has since moved back outdoors, and the males seem to hit their target fine in every other bathroom, so I know there has to be another answer. Recently, we even removed the whole toilet, scrubbed and hosed it down inside and out, scrubbed the floors and wall behind it, replaced the wax ring and reinstalled it. The smell was back the next day. As a last resort, I poured the urine enzyme solution on the whole floor, hoping that if urine had somehow seeped behind the trim or between a crack, that would reach it. All I got was a sticky floor, and the odor persists.

Help! Is my only option to tear up the floor???? I really doubt the toilet ever overflowed, and even if it did, how could a urine odor from a dilute urine/water mix persist this long? Even though we replaced the wax ring, is it possible the odor is still coming from the sewer? There doesn't seem to be a place I can pinpoint the smell--it just seems to be all over. What to do next???