Okla. Stat. tit. 15, § 15-63: Mistake of fact defined

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.