Mr. and Mrs. Mitchell, the owners of a small secondhand store, attended an auction where they bought a used safe for $50. The safe, part of the Sumstad estate, had a locked compartment inside, a fact the auctioneer mentioned. After they bought the safe, the Mitchells had a locksmith open the interior compartment; it contained $32,000 in cash. The locksmith called the police, who impounded the safe, and a lawsuit ensued between the Mitchells and the Sumstad estate to determine the ownership of the cash. Who should get it, and why?