A Lost Load! is a magazine story.
A new section of track is being laid near the quarry and Thomas is to deliver a trainload of metal chairs, used for holding the rails in place, to the workmen. The truck of chairs is coupled behind Thomas' train of sand trucks which he is to take to the harbour. Thomas is pleased to be helping with the new track laying and sets off.
Thomas rounds a bend and starts to climb a steep hill as the sand trucks grumble and groan. What Thomas nor his driver and fireman do not know is that the truck full of heavy metal chairs has not been coupled up properly. As Thomas reaches the summit of the hill, the truck of chairs bounces free and rolls back down the hill. The points at the bottom of the hill had been changed and the truck rolls into a siding and collides with a pile of dry cement. The truck tips up and spills its load onto the ground.
When Thomas arrives at the quarry, where the new line is being laid, the workmen walk along Thomas' train, looking for the truck of metal chairs. They are very confused when they cannot find it.
Meanwhile, Percy is shunting trucks into the same siding that the chair truck had derailed on. It is not long before Percy spots the truck in the pile of cement and dozens of metal chairs scattered all over the ground. Percy's driver soon telephones the Fat Controller who is happy to hear that the missing truck had been located. He calls for the Breakdown Train to go and rescue the chair truck.
By late afternoon, the truck gets put back on the rails, reloaded, and delivered to the quarry once again. At long last, the new line is completed.