Hi FlamingoKicker, I've come up against this too. Have you checked to see if they're still in the manage households as a ghost household? If so you could then merge them into your household or place them in a home somewhere so they don't dissappear and make them eat ambrosia (I'm not sure if you can give townie npc sims it and they'd eat it on their own? ) or if you have the option to make a spellcaster use dedeathify to bring them back to life or if you have the wishing we'll from the garden stuff pack I think you can wish them back to life. I did the merging into household spellcaster thing when my sims best friend died that wasn't in world and I couldn't find their urn anywhere. I don't own life and death or use in game cheats so maybe there's something in there that could do it? Sorry if none of this helps, just thought I'd share my resolution when it happened to me.
