When the goslings hatch, one egg is not hatched. The goose gives it to Templeton, who rolls it underneath the feed trough. He COVERS it with dirt to hide it. Later, when Fern and Avery are at the farm, Avery tries to get Charlott, but Wilber runs into him and throws him into the trough. The edge of the trough hits the UNCOVERED egg and busts it. How did it become uncovered?