B767-300 LOSES PACK ACCESS DOOR INFLT.

Narrative

EARLY AT ACFT FOR WALKAROUND. ONLY THING OUT OF ORDINARY NOTED DURING WALKAROUND WAS TIRES HAD JUST BEEN SVCED; EQUIP WAS AROUND TIRES BUT NO MAINT PERSONNEL. OTHERWISE; NORMAL WALKAROUND. PASSING THROUGH 13000-14000 FT AND OUT OF LCL TFC AREA; WAS DIRECTED TO START BREAK. JUST AS I ARRIVED AT SEAT; HEARD ROLLING BANG SOUND ABOUT 1 SECOND IN DURATION THAT SEEMED TO COME FROM JUST UNDER ME. NO OTHER INDICATIONS NOTED IN BACK; WENT TO FIRST CLASS GALLEY PHONE AS CAPT WAS CALLING BACK. WE DISCUSSED SOUND; I HEARD OR FELT NO OTHER VIBRATION OR ANY OTHER INDICATIONS OF A PROB. CAPT SAID IT SOUNDED LIKE A LUGGAGE CONTAINER HAD SHIFTED IN CARGO BAY; WHICH HE SAID HE HAD HAD BEFORE. I HAVEN'T; AND WITH NO OTHER INDICATIONS OF A PROB; DEFERRED TO HIS EXPERIENCE. WITH NO REASON BOTH IN BACK OR IN THE COCKPIT TO SUSPECT ANY PROB; WE DECIDED TO LEAVE ME IN BACK AND PRESS ON. I DID WALK BACK TO MID GALLEY AND HEARD AND FELT NOTHING UNUSUAL. DURING COURSE OF MY 2 HR 50 MINS BREAK; I DID NOT NOTICE ANYTHING. SUBSEQUENTLY; UPON LNDG; IT WAS DISCOVERED THAT THE #1 PACK ACCESS DOOR WAS MISSING. THROUGHOUT THE 10 HR FLT; WE HAD NO INDICATIONS OF ANY PROBS OR ANY RPTS OF LOUDER THAN NORMAL NOISE OR ANY UNUSUAL VIBRATIONS FROM PAX OR FLT ATTENDANTS.