There are two things you can try. Natures Remedy is a liquid that you pour or spray on full strength. When my cat peed in my bed, I poured it on and when it dried there was no more smell.

You can go online and get Nok-Out, another liquid. My cat missed the litterbox that I had in my closet. He peed on the floor. I sprayed that stuff on full strength and it got rid of the smell.

I hope you get to keep Whitey and get him fixed. He needs someone like you to care for him, not the jerk that doesn't take responsibility for him.

Good luck.