Alright, just got off the phone with the dealership. They confirmed the leak through the 3rd brake light, but I also suffered from the dreaded slider window crack. According to the service department, both would be covered under their respective warranty as my truck is one of the "lucky" ones that got covered for the window crack as well.
I've had some funny things happen leading up to this, that all came full circle and made total sense to me now, so I will share in the hopes that some of you guys can maybe catch this in your trucks before it completely dies and get it resolved without being stranded:
1. Bed light always seemed to go out on one side. Replaced the bulb, then it would die shortly after. (didn't bother me, so ignored it)
2. Random stain on the ceiling above back seats in corners (Thought maybe kids drink splashed up, but now I'm thinking it's from the leak)
3. Battery died about 3 months ago after sitting for a couple of days at an airport. (Blamed it on the cold and thought battery was just getting old as a quick jump start resolved this and haven't had any other issue until now)
4. Truck would tell me the "key fob has left the vehicle" since that initial dead battery, but would still run and start up fine so I just ignored it thinking "older truck, acting goofy since the battery died that one time". (Starting to now think that was the early signs of the RF hub failing).
5. Nasty smell, like spilled milk. (Blamed my kid for spilling milk, as it coincidentally started after a trip to McDonalds. I now believe that was the electrical components starting to fry and owe my son an apology)
6. No power at all. No response from keys, no dash lights. Nothing. Replaced the battery (going back to the thought that it was just old), and got dash lights and interior lights, but no power to start button and wouldn't start at all, didn't even crank.
I'm still waiting for the tech to open the truck up and actually take a deep look, but so far all signs are pointing to the common issue of water leak messing up the electrical components behind the back seats.