The biggest "for sure" giveaway is to go to the analysis page of the ride in question and look at the elapsed time. Dragging the mouse over the graph, the time will suddenly jump, from a few minutes to a few hours. If the speed after the time break is significantly higher, the bike is now in/on a car. The best I've seen was a ride of about an hour and a half, with a total elapsed time of almost 1600 hours. I cannot even conceive how that happens.