From the question, the type of mistake described in which one party made the mistake, is known as Unilateral Mistake. However, Unilateral mistake rarely void or cause invalidation of a contract, except if the nonmistaken party is aware of the mistake or is the cause of the mistake.
However, in this case, the nonmistaken party is unaware of the mistake and is not the cause of the mistake, then it is generally expected that the court will hold that contract is VALID.
