A teenage girl was struck and killed by a subway train in Queens Sunday afternoon as she tried to retrieve a cellphone from the tracks, authorities said. The FDNY was called to the 63rd Drive-Rego Park stop on the R Train around 1:50 p.m. Police said the girl who was struck by the train was 13 years old. Her cellphone had dropped onto the tracks and she was reaching for it when she was hit, police said.