I"ve seen a vet, thanks.
He does this occasionally when the litter boxes have been used. They also spread litter all over the place, and I'm not very good about cleaning it up (probably once a month). It's a bit embarassing to say this, but often the area around their litter box looks like a beach. That's what we call it, "the beach." It probably looks like one big litter box to him.
I thought perhaps if I put wax paper down it might be easier to keep it clean, as I could pick up the paper and dump the litter. And if he did go outside the box, it would easier to clean that up too.
So that is the longer story on why I was wondering about it.