So, you're authenticating yourself, and searching other non-publicly-searchable people's ID? Or you're authenticating, searching your own, and seeing people who don't list themselves as public? Or, you're seeing people who aren't public, but in your friends list, and you're publicly searchable?

If it's the first, then that's definitely a problem, as anyone can be a FB user. In that case, care to post the command somewhere? This should be made known, as it's definitely a privacy concern, and FB tends to do nothing unless threatened.