SDCL § 22-30A-6: Theft of lost or mislaid property.

Any person who comes into control of property of another that the person knows to have been lost, estrayed, mislaid, or delivered under a mistake as to the nature or amount of the property or the identity of the recipient, is guilty of theft if, with intent to deprive the owner thereof, the person fails to take reasonable measures to restore the property to a person entitled to have the property.