To bring a happy end to this tale - Zombie Carl has been returned to his home with me. THANK YOU to Grimp0nd for helping to spread the word, and to Doctor Cogstein for providing exactly the right information to be able to locate him. Once I was able to talk to a high enough coordinator in the KidsZone area, they got on their radios, passed the right information along, and another coordinator hand delivered him to me in about 15 minutes. Honestly, the Universal family, even the ones I haven't met, are just amazing and fantastic people.
To bring the tale even more allure - it turns out Carl was found in La Llorona. I'm thinking, since La Llorona steals children, that she grabbed him from my waist belt as I was going through, in order to drown the poor child. Unfortunately, with Zombie Carl being ALREADY dead, her efforts were for naught, so she angrily tossed him to one side, where he was stumbled upon by a confused Team Member.
And THAT'S why you need to stay in the house during the Zombie Apocalypse, kids!!