ugh yeah that happens to me too, though I never bother checking the campsite when it happens. with my luck it would be a cool villager or someone I'm actually looking for vv
No because I am terrified of this happening so badly I always make sure that one unfavoured villager leaves when I get ten, even if I'm not quite ready to let them go.
I haven't had that a lot, because my town standardly has 9 villagers - the campsite is my only way to get a tenth. I would only convince a villager that I like to move in, so the tenth doesn't come in easily and if I get a new villager in the campsite before the next villager I don't like moves, the chances are little I want that villager anyway. I don't really have a 'list' of villagers I want to have living in my town, I just take in who I like and move out who I don't; so such disappointments usually don't happen to me.
Yes, I've had it happen three times - Marina, Merengue and Fang. I've since had Marina and Merengue move in from other towns, still hunting for Fang though. It's such a terrible feeling, I never check my campsite when I'm full anymore because I hate the disappointment!