The problem is a loose nut in the rudder mechanism, but is it right to assume there are an abundance of fasteners in the rudder system, and failure critical fasteners are wired? In this case the nut was missing (bad) but the plane did not crash (good). The problem was found upon inspection and Boeing notified. Boeing immediately checked planes in inventory and found one fastener not tightened to spec. Since the bolt was found during an inspection, and apparently the airplane had not experienced a control problem, is it not likely the bolt was not safety critical for some reason? Are there not hundreds of bulletins issued by all manufacturers every year to follow up on something unusual found during routine maintenance?