We don't expose our database publicly and we have no discovery mechanism. Also I don't believe unlisted videos are considered to be private. There is a private

We don't expose our database publicly and we have no discovery mechanism. Also I don't believe unlisted videos are considered to be private. There is a private setting which disallows for public to see such a video. And finally, it's not very trivial to touch 5.5 billion videos often enough to see if any of those became unlisted.