So at some point during my trip to Saarbrücken for the qepHom last November, I managed to disabled the WiFi on my laptop. It has a hardware switch with an LED, and it somehow got into a state where it was permanently off, and clicking the switch didn't switch it back on.
I couldn't enable WiFi from Network Manager because it said it was disabled by hardware switch ... but I had no idea how to get it working again. I was even considering reinstalling on the off-chance that that might fix it.
tl;dr: after installing "rfkill" and running
rfkill unblock wifi, the LED started flashing, I got asked for my keychain password, and I was connected to my home WiFi network! Yay!