Without any control of your UTH, and considering the short amount of time (relatively) that you would have been on vacation, I'd say a burn is a pretty easy conclusion to come to. Follow the advice above regarding thermostats and thermometers, and no more soaking until he has healed (water+scabs=poor healing). You can wipe him down with a Betadine solution on a gauze pad or paper towel if you wish, but do not soak him.