Cable and internet are back
I'll give this AT&T service guy credit -- he called the right number, admitted that the other guy goofed, and fixed the problem (although he has no idea why the signal was gone). He ended up replacing the main box, the face plate in the wall, the coax to the wall, and a part outside of the house before it came back on. But it is back, and that's what matters. Now the next fun part -- calling the billing department to get credit for the lack of service for two days.