WINONA, Minn. — A tracking system that the First Student school-bus company has on all its vehicles failed when a Winona school bus driver got lost on the first day of school. Unclear was whether the driver had failed to activate the on-board Zonar device or inadvertently turned it off. When a company dispatcher realized the bus was missing, a supervisor went looking for it. It is known that First Student has had a driver shortage. Drivers were being hired at the last minute, some lured by a $3,000 signing bonus and pushed through hurried emergency training sessions. When the supervisor found he bus, mayhem erupted, according to a mother who separately had been searching frantically two hours for her child on the bus.