Is there a way to reactivate a sim that was taken away?

I've had a child taken away once, and that child stayed forever in the family tree, and did not age at all.  I looked for him in the NPC households but could never find him.  Since he was a tot I could never phone him either. Gone , nothing but a memory.

 If anyone had a relationship with yourmissing sim, maybe try calling her on the phone? But for some reason i think she is probably lost forever.

I think your only chance will be what  GameGirl2168a  suggested.