I have now convinced myself that I shut off the heating to my house before I left.  I changed air filters and cleaned out the contraption the night before leaving, even though I planned on doing that well beforehand.  Of course, after re-installing everything, the thing I would have to do next is go back up and turn the thermostat back on.  I think I did that ... but knowing me, I didn't.  Maybe not hearing the heat turn on all night would have been a sign something's wrong, but I cranked up my own heater, so maybe I wouldn't have noticed.  Besides, I was distracted with finishing packing, and shutting off the main, and turning down the water heater.

I need to strenuously ask my uncle to drop by the house.  Before it was to make sure there's no water leak in the basement and possibly to water the plants.  Now, I should ask him to check if the thermostat is set to Auto.  Because while it's cold now, highs will creep closer to 0 in the next week or so.  If I stupidly shut off the heat, I don't think it's too late (crosses fingers) to turn it back on.  But if I wait, or if my uncle waits ... my God, then I'll be homeless.