From an air traffic controller's point of view, I too am bewildered as to how this can happen.
Does anyone know whether when flying into Branson you do so under a radar service or procedural service?
If the aircraft was under a radar service, how on earth did the radar controller not notice!?
If it was on radar, I imagine the aircraft was released from vectors to fly a visual approach. But that still doesn't mean the controller can forget about monitoring it on radar.