WILSON, N.C. — The crew of a truck carrying a load of gold bars had just pulled off the interstate in North Carolina when, the two men told police, a seemingly ordinary episode of carsickness turned into a multimillion-dollar heist. On Wednesday, authorities said they were suspicious that the roadside robbery might have been an inside job. As soon as the guards stopped on the shoulder because one of them wasn’t feeling well, three robbers drove up in a cargo van and confronted them at gunpoint, yelling “Policia!” and ordering the crew to lie on the ground.