I guess, this concerns every stackexchange site.
It sometimes happens that I ask a question which is answered, but not satisfactorily. I then have the option to put a bounty on this question. But I made the experience (on another stackexchange) that even then there will be no satisfactory answer.
I think it would be a good idea to add a button for “Unaccepted” answers in the “Unanswered” section. Or – since there are users just don't accept answers out of laziness or something – it might be even better to allow users to explicitly mark their questions as “unsolved” or “unaccepted”. That way they still have a chance to get some (permanent) attention which is needed for them to be solved by someone.