This is a new one!
My sim just got married ( by eloping) to fulfill the inheritance conditions.
But he was a random sim so I wanted to change him in CAS
I go to CAS ( Cas.fulleditmode first) and he isn't there.
Moreover, he isn't in my save anymore at all! And my sim doesn't know him!
I did the merge household after the marriage and moved him in and his 20k.
The 20k is gone too, but the inheritance is still there ( phew).
Very odd though. Now it's just her and the cat again. She lives on a residential business lot and that's where they got married too. He was added to the family, but going into CAS made him go poof!
On PC, mods have long since been removed and its a new Sims4 folder.