That there is another breaker in the attic for the furnace.
My heat failed in the wee hours of last Saturday. Luckily, the weather was nice last weekend, so I didn't have to get an HVAC tech in to fix it. I called this morning and described my problem.
The tech had it fixed within a few minutes. He said that, even though the breaker didn't look tripped, he flipped it on and off anyway. I had heat and AC. For $85, that lesson will stick with me.