So we took it into the garage and the mechanic poked at it for a while and figured that what must be going on is that the key cylinder was old and sloppy and would let you pull the key out even when it was in the "accessory" position. So we replaced the key cylinder, and now we have two keys, one for doors and one for the ignition, yay.
And then it did it again, stranding Jerry at work. So we took it back in, and the mechanic looked at it again, and determined that its electrical system is pretty weird. (His theory is that it's because it was manufactured in Canada and has extra stuff in place for things like daytime running lights, which are for the Canadian market.) It stopped misbehaving after he fiddled with the blinker module thingy (which normally has three prongs, but in this case has NINE), so he replaced that and we crossed our fingers.
But then the other day I pulled into the garage and the lights started flickering again. So I pulled it back out and drove to the grocery store, and by the time I got back home it had stopped.
We were planning on taking it back to the garage this morning, but I feel like it's throwing good money after bad. Not that I think the mechanic isn't honest or competent -- I know that car repairs can sometimes be a matter of trial and error, and he only charged us for one hour of labor last time, even though he put a lot more into it -- but each trip in costs a decent chunk of money and it gets less and less likely that it's going to turn out to be something cheap and easy to fix, and more and more likely that it'll be a repair that costs more than what the vehicle is worth (which is not a lot at this point), and if we're headed in that direction, I'd rather just start saving up money to replace it entirely.
So instead, this morning I went to AutoZone and spent $25 on a little knife-switch type quick disconnect for the battery. I figure that even if the electrical system continues to misbehave, there's no way it can drain the battery while it's parked if it's not physically connected. So now we'll just have to spend an extra 30 seconds to pop the hood and flip the switch open or closed every time we drive it somewhere. Ultimately, that's not such a hardship; fingers crossed (again) that it will suffice.
Weekend update: Star Wars on Friday night; pickled more crabapples on Saturday and made sunomono for the