First up, the office outlet.
I started by taking a look at the service panel labeling, and found four breakers labeled "downstairs lights." No help there. So I grabbed my circuit locater (which has less than a 100% track record since it never properly located that all of the GFC protected outlets in the Bartlett house were on the same circuit) and gave it a try. The first circuit it located was wrong. So onto plan "C," turn off breakers until I find the right one. I tried all of the downstairs lights, and two of the appliance breakers and one for "back porch" with no bigger effect than worrying robot_grrl that I'd leave her in the dark for her shower. Finally I located the circuit - labeled "garage." Oddly this one was also located by the circuit locater which was pinging that breaker consistently while it kept giving false positives on others, but inconsistently.
But when I got into the office, I noticed that the UPSs for my computers - plugged in on the adjacent wall - were back on. Apparently they are on a different circuit.
The fix wasn't too hard - the ground wires were not properly into the screw. I did have to trim them and then clean some paint or drywall texture off of them before I got them wrestled into place. I also was, at least for this outlet, relieved of my worst fears - that I'd find aluminum wiring in non-aluminum rated fixture - since all of the wires I could see were copper.