The cause of the crash that killed airborne traffic reporter Bruce Wayne earlier this month may never be known, because critical evidence was lost in the fire and explosion that destroyed Wayne’s plane after it slammed into a parked truck, said the chief accident investigator for the National Transportation and Safety Board. Wayne, 52, had just taken off from Fullerton Municipal Airport on June 4 to begin his morning reports when his single-engine Cessna Cardinal began experiencing engine trouble. “The backfiring and misfiring described by some witnesses would indicate an ignition problem,” said Don Llorente of the NTSB’s Los Angeles office. “But others described it as sputtering, which might mean fuel contamination or some other fuel problem,” he added. “Of course, all those items to check were destroyed by the fire.” Llorente said the investigation has also been hampered by the lack of maintenance records for the plane.