I work in a vets. You need to pat up but not rub what's there. Sprinkle with bicarb to soak rest and hoover up. Then use biological washing powder (not non-bio! ) 10% solution with warm water, scrub, dab up, leave to dry and then sprinkle bicarb again, leave for a few hours and hoover up. If it's the same spot each time he can probably smell it from last time, if it's different spots it's more difficult to stop him