Final answer:
The specific surprise attack foiled by Wentworth Cheswell's contribution is not detailed in the provided information, but it may be related to British military failures around the time of Lexington and Concord in 1775.
Step-by-step explanation:
The surprise attack on the colonists that was ruined as a result of the contribution of a free African named Wentworth Cheswell is not directly mentioned in the provided information. However, discussing events around the same period, such as the actions at Lexington and Concord on April 19, 1775, where miscalculations and mishandling of communications led to failures in preserving peace, it is possible that Cheswell's contribution could be related to a similar instance of foiled British military plans. Wentworth Cheswell is a notable figure in revolutionary history, being the first African American elected to public office in America and serving as a town constable, significantly contributing to his community and possibly the war efforts against British forces.