Hello,
In case you are still in need of vanishing villager scenarios, I just had one . I had an adept researcher find the graveyard, then go and bury the only dead body there was. When he was done, and leaving the graveyard, I switched his preferred skill to "healing". I knew I would need another good healer since the best one I had was getting old. I then dragged him to the cactus where he promptly disappeared. My village population went down by one. Then when I checked my stats it said that 2 villagers had been buried. Sure enough, when I went back to the graveyard, there were two headstones.
I'm still early in the game, with only 93 hours played. My max # of villagrs is 12. I'm playing on a Tungsten E.