The reason why this is happening was because he still smelled his pee on it. So the first thing we have to do is to remove or replace the faintest scent of ammonia. Ammonia is sometimes found in cleaning products and DOG PEE which means you'll have to scratch those from your list when dealing with a puppy puddle. The moment he smells ammonia he'll think, "Oh that's where I left my liquid present. I'll go back there to leave some now!"
To block the smell of ammonia, pour vinegar on Fido's pee and be prepared to use towels, paper towels, newspapers or a mop. My vote's on the paper towels. I used up all of my mom's tissue paper (*^_^*).