They were checking out the wiring when it started working correctly, though, so they're thinking that the "fix" was a connector somewhere being reseated when it wasn't exactly right before. They don't want to give the car back to me only to have it break down again, so they're going to try starting it up after letting it sit overnight and go from there.
It looks like I'm driving the Sonata for at least one more day, but I agree 100% with the reason why.