Police say that Jason Callahan, 19, from Myrtle Beach, S.C., was reportedly following the Grateful Dead when he was involved in a fiery car crash and killed instantly. He was burnt beyond recognition, and since his family never reported him missing, no one claimed his remains. All he left behind were the tickets, and a letter addressed to "Jason." The only identifying information: a star tattoo, according to a New York Times account. The paper lists a number of amateur investigators on Reddit, Websleuths, and Facebook, who, armed with these few clues, sketches and a composite image of the victim,...