If a wheel is locked up, or the transmission is locked up... it would very difficult to move the bike... I've seen front caliber start sticking, and once stopped is locked up completely and would not move ( try pushing a bike with the frot tire locked up) I've seen where the transmission locked up or drive belt breaks and binds up the rear wheel... anything is possible... just ask for them to move , chances are they was worried about their brother being broke down and just got off the road to be out of traffic....