[Open] - Passive Sims disappeared from house and no longer exist/are related

This just happened to me too. A passive sim was in the middle of an event (arch-nemeses) with one of my active sims and then I open the app and my active sim was still in the event but the passive was gone. Like completely gone as if she never existed. Gone from the family portrait too but there's still space there, they're standing like she's supposed to still be there. Chapter 5 (?) relationship completely gone.