The parents of Britney Gengel, the college student from Rutland still missing after the Jan. 12 eathquake in Haiti, returned home yesterday from a nine-day vigil at her Florida campus after hearing from the US State Department that the mission has shifted from rescue to recovery, leaving slim chances of finding any survivors. “They will start pulling the building apart layer by layer,’’ Leonard Gengel read from a statement yesterday at Logan International Airport, referring to the hotel where his 20-year-old daughter had been staying when the 7.0 earthquake hit. His voice breaking, he said, “We are asking our government...