What was found
THE ACFT LANDED AND WAS PROCEEDING DOWN THE RUNWAY NORMALLY UNTIL THE PILOT APPLIED THE BRAKES IN PREPARATION FOR LT TURN ONTO TAXIWAY, THE ACFT STARTED TURNING TO THE LT AND PROCEEDED OFF THE RUNWAY AND DOWN AN EMBANKMENT JUST BEFORE THE TAXIWAY TURNOFF. THE PILOT NOTICED THAT THE RT BRAKE FELT SPONGY AS COMPARED TO THE LT. AFTER INSPECTING THE BRAKE ASSEMBLIES, IT WAS NOTICED THAT THE BRAKE LINE FOR THE RT SIDE BRAKE (NR 4 UNIT) WAS NOT ATTACHED TO THE BRAKE ASSY AS THE B-NUT WAS MISSING FROM THE HOSE. A SEARCH WAS CARRIED OUT FOR THE B-NUT BUT IT WAS NOT FOUND.