REFUELING PANEL DOOR LEFT OPEN -- BROKE AND CAUSED DAMAGE INFLT.

Narrative

FLT ANC-SEA DIVERTED TO BOEING FIELD WHEN SEATTLE WENT BELOW CAT II MINIMUMS. ACFT WAS REFUELED AND DISPATCHED TO SEATTLE. AFTER ARR IN SEATTLE IT WAS DISCOVERED THAT THE REFUELING PANEL DOOR HAD BEEN LEFT OPEN AND REFUELING CAP WAS MISSING. THE FUEL CAP SEPARATED FROM ACFT AFTER SCRATCHING AND POUNDING THE UNDERSIDE OF WING. THE INCIDENT STARTED WITH BOEING FIELD GND PARKING US ACROSS THE ARPT ON A TXWY; SO WE HAD LIMITED SVCS. (WE HAD TO USE THE FUELER'S LADDER TO GET ON AND OFF THE ACFT FOR PREFLT; AND RELEASE PAPERWORK. THE B737-200 IN ALL CARGO DOES NOT ALLOW ACCESS TO REAR STAIRS WITH LARGE CONTAINERS.) AFTER RECEIVING PAPERWORK AND DOING WALKAROUND; THE FUELER ASSISTED ME BACK ON THE AIRPLANE WITH THE USE OF HIS LADDER THROUGH THE FORWARD ENTRY DOOR. AT THIS POINT HE MUST HAVE FORGOTTEN TO CLOSE THE REFUELING DOOR. IF WE HAD A GND CREW FOR ENG START; THEY MIGHT HAVE CAUGHT THE DOOR OPEN. ALSO; 1 OF OUR 8 B737- 200'S HAS A REFUELING DOOR OPEN LIGHT ON THE OVERHEAD ANNUNCIATOR DOOR LIGHTS. THIS MIGHT BE A GOOD TIME TO INSTALL THE REFUELING DOOR CAUTION LIGHT ON THE REMAINING B737'S.