Okla. Stat. tit. 58, § 58-81: Proceedings in case of lost will

Whenever any will is lost or destroyed, the court must take

proof of the execution and validity thereof and establish the same,

notice to all heirs, legatees and devisees being first given, as

prescribed in regard to proofs of wills in other cases. All the

testimony given must be reduced to writing, signed by the witnesses,

filed and preserved.