You can't see a villager that is in your void. The past residents of your town that appear on Main Street are not in the void they are just visiting you.
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The system "Remembering" your past 16 villagers is not the same as having villagers in the void. The void is where villagers, who have moved from your town, are waiting for a new town, with space for them. Villagers waiting in the void who move to a new town, will talk about coming from your town and will hum your town tune. Once you "clear them from the void" after you visit a town with 10 villagers or host someone who has 10 villagers, they are gone and anyone visiting you or connecting via streetpass will not get one of your old villagers.