Seller did not disclose strong smell of cat urine

[David S.]

We recently purchased a home that seemed to smell fine when we walked it, albeit with a scent diffuser plugged in. After taking possession the smell of cat pee is quite strong, especially on hot and humid days, with no diffuser to mask it. Apparently they became quite good at masking the smell and likely aired the home out before we arrived. In hindsight they were in a hurry to get back into the home after we walked it under the guise of an ailing father who needed rest. I suspect they were worried we’d catch on if we took too long. 
All the neighbors are aware this house used to be “the cat lady’s” years ago, with dozens of cats. (Lesson learned; talk to neighbors every time.)
We also have a seller’s disclosure that states there are no pet smells. 
At this point we will have to remove the floating engineered wood floors, rip out the flooring beneath (suspect original wood floors), seal, then put in a new layer, then reinstall the wood floors after sealing the bottom of each plank, then seal the lower part of the walls, then repaint. This will take us many days and cost us thousands in materials and time. 
What recourse do we realistically have here? We’re looking at going to mediation first and foremost. 
Thanks