Meaning
completely gone? As in his entire existence wasn't recognized by the game in sims' memories or anything? Or do you mean he just wasn't on the lot?

Usually, you can just either call the sim, or summon him with The Summoner. (included with the InSIMenator) Seeing as this happened to me once, I also had to ask that sim to move in with their spouse afterwards, so that they'd officially be apart of that household. :lol: