I carried the boy into his room, helped him get dressed and then followed him to the kitchen as he ran to get paper towels. In the 4 minutes that we were away from the puddle, it vanished. Completely gone. No trace of moisture, no scent of urine.
No one else was home and it couldn't have evaporated. The boy has witnessed the small puddle and, too, wondered where it had gone. And although there are many a times that I have placed wishes for these kind of messes to go away on their own, it's a little freaky when it actually happens.