You're right. Your situation is unusual. We hear far more stories of managers who try to micromanage their staffs. But obviously, too much or too little supervision isn't a happy situation for most of us.
As a first line of action, you should immediately request a formal appointment with your boss to outline your goals and objectives for the next six months. Before the meeting, write down four or five tasks or projects you'd like to undertake and the two or three performance criteria he'll use to measure your performance. That way, if he can't or won't give you direction, you can make suggestions about how to proceed. Be sure to follow up this meeting with a written letter or memo outlining what was agreed on and how you'll report your progress.
Second, if you can't get satisfaction with this approach or if you feel too uncomfortable with little or no supervision, you may need to find a new job. In the meantime, try to make the most of the situation and learn what you can. Fortunately, it isn't uncommon to hear of job "mismatch" situations these days. Some career counselors talk of the one-third rule: One-third are happy with their new jobs; one-third want to move to another position within the organization; and one-third want to quit. If presented carefully during interviews, by discussing your insights, personal development and accomplishments, you can diminish any negative impact from this experience.