I'm not sure but I think the option is reserved for Sims that live outside of the lot you live on.
In that way, it would be akin to trying to invite your wife for a sleepover - it wouldn't make sense in game terms.
You should be able to reset the Sim if he has disappeared somewhere:
Press Ctrl+Shift+C ingame and then enter "reset sim [first name] [last name]"(replacing the [**] [**] with your Sim's name), I think that should do the trick?
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