WASHINGTON - The United States played a crucial but almost "invisible" role in finding and killing Abu Sayyaf leader Abu Sabaya by using a tracking device sewn into his backpack's fabric and plotting his movements with unmanned Predators and high-flying surveillance aircraft, The Atlantic magazine reported.In an article in its March issue, the magazine said the Central Intelligence Agency (CIA) and the US military targeted Sabaya, whose real name was Aldam Tilao, and his group after they kidnapped American missionaries Martin and Gracia Burnham and another American Guillermo Sobero in May 2001 holding them for ransom. “His removal by Philippine...