Did you have any condensation on your windshield? My dash put on a similar light show after I slept in my truck cab on a below-freezing night in the mountains. The condensation probably rolled down into the BCM.
When I drove the the next day, I turned the on the heat, fan, and AC to max, rolled down all the windows, and drove for a while. My dash continued flashing and beeping until I turned the truck off and back on, after driving for 15 minutes or so.
The CEL stayed on, but the dealer cleared the code and found no problems. This was well over a year ago, and I've had no problems since. So the condensation appears to have caused no permanent harm in my case.
You mentioned no water on the carpet; also check the headliner, especially near the rear window. That's a notorious leak point on our trucks. Behind the back seats is the RF hub, which might also be a source of light show magic.
