Last night, my daughter's room was very cold. We noticed this at roughly 1 in the morning. Christie wondered if the vent might be closed, but I had noticed that the heater was not running, and that remote sensor for the thermostat showed a low enough temp that it really should have been. It turned out that the thermostat wasn't picking up the signal from my daughter's room, so it didn't know to run the heater. So I turned the heater on manually and proceeded to troubleshoot the thermostat.
I had to download the manual, take a couple of things apart, swap out some batteries, switch the channel the signal was running on, and try to figure out why the batteries fresh off the charger still triggered the "low battery" warning on the thermostat. I resisted the urge to try and diagnose the battery charger.
Meanwhile, Christie came out and told me that the vent was indeed closed.