18 Pa.C.S. § 3924: Theft of property lost, mislaid, or delivered by mistake.

A person who comes into control of property of another that he knows to have been lost, 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, he fails to take reasonable measures to restore the property to a person entitled to have it.