I seem to have solved it, so in case anyone else runs into this problem, I'll explain how. No one likes a "nvm solved it".
I figured out which lords were missing by asking the ladies that had taken up permanent residence at my court who their relatives were. Then I used the save game editor to change slot_troop_occupation (2) from 0 to 2 on those three missing lords. I think all three of them had slot_troop_prisoner_of_party (
set to 26, which if I'm understanding it right should be a Jatu army. Having used cheats to check the entire map several times, I can confidently say that no Jatu armies had them as prisoners. I set that value to -1. They now show up on the list when asking people for the location of someone, and should begin spawning shortly after.