Other mistake: Henry was supposed to take Emily's trucks to the Coaling Plant, but he takes them to Knapford Yards instead. The narrator also refers to Knapford Yards as the Coaling Plant.
Continuity mistake: When Salty gets blocked by the trucks, his face increases in size.
Answer: Butch the breakdown truck must have pulled Gordon's tender all the way up the rails so the breakdown train can reach it and also Butch helped to get Gordon close to the winch.