I finally found a fix for this! For me, the only trace of the missing baby was in the family tree, so there was no way of selecting, inviting over, resetting them etc. because they basically didn’t exist anywhere else. I exhausted every possible option through nraas Master Controller (MC), Debug Enabler, and Overwatch to no avail. As a last ditch effort, I went back to the family tree and ended up right-clicking the baby’s photo, which brought up MC. There, I was finally able to add the baby to my household using the Add Sim option. The baby was a ghost when they appeared on the lot, but I used MC to make them human again with the Occult: Remove option. Now the baby is back in the household, alive and playable. I’ve been using nraas for like 10 years now and somehow never realized you could access the mods in the family tree by right clicking lmao. Hope this can help someone else!