Warhorse, already done that. That's how I got the zinger when I brushed the hot terminal.
As for the GFCI, there's only one GFCI in the house, in the basement. It's fine. It powers the FIOS box. If it trips, my cable, phone, and internet go out.
House was built in 1979 by Drunken Monkey Home Destrxtors. The LOL Cats could have done a better job.
"Disconnect the offending wires at both ends, twist one end together, read for continuity at the other."
That would be great if I knew which breaker served the other end. The damned box isn't labeled all that well (read, the only labels are the ones that I put in myself).
I've been telling myself that one of these days I'm going to do an electrical mapping on the entire house, but haven't gotten there yet. Maybe that's a project for tomorrow, or as soon as I get the box fixed.
The bird dog is a great idea. I'll look at picking one up.