CHARLOTTE, N.C. — Determined to learn exactly what caused his mystery illness in 2011, Trevor Bayne made repeated visits to the Mayo Clinic over the last two years, asking questions about his health and medical history. The youngest winner in Daytona 500 history wasn't sick and he wasn't suffering from any of the symptoms — nausea, fatigue, double vision and numbness in his arm — that had sidelined Bayne for five races in 2011. He just wanted an answer.