Blair Hamrick left for Colorado in 1993, an ambitious University of Tampa graduate headed for a six-figure job as a pharmaceutical sales rep. He returned with no job, no money, no explanation. “I come back with my tail between my legs, can’t tell anybody why, and people say, ‘What’s wrong with him?’ ” he said. Now the truth is out: Hamrick was one of the GlaxoSmithKline whistle-blowers whose firsthand revelations about off-label prescription drug marketing helped lead to the historic $3 billion settlement announced Monday.