B777 Captain reported ground damage occurred when a coupling ruptured during fueling and damaged the upper fuselage skin. The aircraft was removed from service for repairs.

Narrative

Parked at Gate 3 in ZZZZ; 30 minutes prior to departure a Gate Agent came down and asked if it was OK to board because he heard there may be a fuel spill. There was no fuel truck present and no spill so we boarded the passengers. Boarding was done about 20 minutes later and a truck had shown up during boarding and fueled us. Approaching departure time the First Officer and I were not aware of the problem until a mechanic came in with pictures of a dent on top of the fuselage; high above the last passenger window on the right side. He said something to the effect that the aircraft should not be pressurized and should not be flown. Right behind him were investigators requesting the Airworthiness certificate; Insurance; and they wanted pictures of our licenses /Medical cert.. We complied with their requests; deplaned; and I made a logbook entry. Later in the day while we waited to DH (deadhead) back to base; we were able to get some more details. Apparently the first fuel truck that came was parked about 15 ft. off the end of our right wingtip when it had a hydraulic system burst propelling a coupling piece 35 yds. and ricocheting off the top of our fuselage. That truck left and the driver reported the event. A different truck fueled us later. I guess there was an assumption that somebody had already reported it to us. There was a meeting going on somewhere so there was no one around to key us in that there was a problem. I think mechanics should check in with the pilots first or at least stop in to see the logbook.