Victims have been found with no identification documents at all and in one case a stolen ID. Remote villages lack phone service to reach family members and determine the whereabouts of missing migrants. More than a day after the discovery of a stifling trailer in San Antonio, Texas, where 53 migrants died after being abandoned in the sweltering heat, few identities of the victims have been made public, illustrating the challenges authorities face in tracing people who cross borders clandestinely.