28-2-409. What constitutes mistake of fact. Mistake of fact is a mistake not caused by the neglect of a legal duty on the part of the person making the mistake and consisting in:
(1) an unconscious ignorance or forgetfulness of a fact, past or present, material to the contract; or
(2) belief in the present existence of a thing material to the contract which does not exist or in the past existence of such a thing which has not existed.