I'm going to go out on a limb here and say that this might be a result of having nine sims living on the same lot (thanks to BoilingOil), as there were some other oddities that I had to Blender away... all the kids were in adult "levitation" mode, and nobody was related to each other. That part was easy enough to fix, albeit a bit tedious.
Here's the situation: Lucius Vorenus, who I've given a "junior officer" rank in the military, is off at work as I enter the lot. After the sun has set and risen again, I realize he hasn't come home... easy enough to overlook with everything else I was dealing with. I look at his job tab to see when he's due home, and it says he's unemployed (even though the little "tank" icon is over his portrait. I try everything I could think of. I tried "summoning" him with the Blender, but as he was technically a member of the household, he wasn't available - only other families show up there, apparently. The Batbox seemed like the most obvious tool for this sort of thing, but I couldn't figure out what part of it to use. Later, I noticed one of the kids heading out to the street when he should've been hitting the sack (a school night). Sure enough, he was going to ask Vorenus to read him a bedtime story, as he happened to be standing out in front of the insula (his key had vanished). Now that he's home, I can fix his unemployment problem, along with straightening out some facial features that I've been meaning to get to. But I think he just happened to be passing through, and... what should I have done if he hadn't? How do you get family members to return home when they're seemingly stuck at work?

The part of the batbox you want is "Force Errors.../On Off-World". Make sure to turn off testingcheats first, or else you'll have to click "reset" a whole bunch of times as it asks you what to do with every single off-world object. Sims who live on the lot but are not present are being held "off world" and that's why they can't be summoned because they're still technically on the lot, they're just in this kinda... non-space where they don't occupy a specific tile. If an off-world sim gets reset, they appear next to the mailbox. It sounds like your sim might have also got reset for whatever reason.

I don't know if that will fix the weirdness with him showing up as unemployed. I once had a very similar thing happen to a sim after I was messing around with the in-game debug object Tom's Clothing Tester (I wanted to look at all the career outfits, but I think it did something weird and overwrote part of the sim's job data or something? She was showing up as unemployed, but the carpool would come and she'd go to work and then never return.) That one I wasn't able to fix until the family had moved out of the lot.

Since discovering the SimBlender, I don't typically play with the testing cheats enabled. I did in fact try that command from the Debugger, so I guess I probably actually made him reappear, and just didn't notice him standing out there right away. I forgot that when they get reset, Sims will tend to remain idle until you give them new instructions. Thanks!