Buy a hamper with a lid. If he can’t get to it, he can’t pee on it.
Sometimes my cats will confuse a plastic grocery bag on the flood with a place to pee. The only solution I found is to keep the tempting items off the flood.
I’m glad you’re having them checked. One of my cats started with piles of laundry, progressed to plastic bags as well, then got in the habit of peeing on anything left on the floor. When I finally took him to the vet he was in kidney failure. I felt horrible to think of the times I yelled at him for peeing on things when he wasn’t naughty, he was sick.
