I've read that even after you've done the 16 villager cycle, the only way to get a villager back is to get them from somebody else when they're in boxes. I know because I've tried to plot reset and campsite reset for beau after I lost him. I had cycled through like 18 villagers and his plot never showed up in my town or in my campsite, and I had gone through every single lazy that had not lived in my town already, and there weren't many left. I had cycled a lot of villagers at that point.