A vital contact in the the Gardner Museum heist has disappeared
                                
                                
                                    (Newser) -
                                    A detective trying to solve the world's biggest art heist has a problem: his key contact is gone—which puts an estimated $500 million in stolen art by the likes of Vermeer, Rembrandt, Degas, and Manet even further out of reach, the  Guardian  reports. The sleuth, Charles Hill, is...