Added to this slight breach, another circumstance greatly contributed to the execution of Wolfe's plan: on the night of the landing, the French were expecting a convoy of provisions. On September 12, Bougainville stationed at Cap-Rouge, received a message asking him to do everything he could to allow these supplies to sail past the British ships and reach Québec during the night. Food was greatly needed in the town and in the camp at Beauport. All posts west of the St. Charles River, including the Samos battery at Sillery, as well as the detachment of Captain Vergor on the Plains of Abraham overlooking Anse-au-Foulon, were warned not to attempt anything that could hinder this operation. Well, the operation was eventually cancelled, the problem being that neither
Bougainville nor the men manning the posts under his command had received the information. This lack of communication had serious consequences because it facilitated the approach and landing of the British troops at Anse-au-Foulon...."
Source: Government of Canada