Mr. Meyer bought a new Shabbos overcoat, 100 percent wool. He had it checked for shatnez and put his name on the label.
One Friday night, when davening was over, Mr. Meyer realized his coat was missing from the coat rack. Nearby hung a similar coat. He waited to see if somebody would claim it, but the shul emptied and the other coat remained.
“I guess that someone mistakenly exchanged coats,” Mr. Meyer said to himself. He left the coat there, hoping the other person would return Shabbos morning or the following week. He checked the coat rack weekly and posted a sign in shul, but his coat did not return.
After a month, Mr. Meyers decided to take the other coat home. “Otherwise, this coat is liable to get lost,” he reasoned. “This way, if the other person ever returns my coat, I’ll be able to return his.”
Pesach arrived, but Mr. Meyer’s coat did not return. “I guess the coat is gone for good,” he finally told his wife.
The following winter, an acquaintance, Mr. Goodman, asked Mr. Meyers: “Did you ever check shatnez?”
“No,” replied Mr. Meyers with a puzzled look. “Why do you ask?”
“Last February I bought a woolen coat on eBay,” Mr. Goodman said. “I saw your name on the shatnez label.”
“You’re kidding!” exclaimed Mr. Meyer. “That’s my missing coat! Someone exchanged coats with me last year in shul. Funny that it wound up in your hands!”
“Please take the coat back then,” said Mr. Goodman.
“But you bought it in good faith and paid for it,” said Mr. Meyers. “It’s yours!”
The two decided to approach Rabbi Dayan.
“Who does the coat belong to?” asked Mr. Meyers. “What about payment?”
“When someone takes an item belonging to another, the owner retains ownership of it,” replied Rabbi Dayan. “The thief has a mitzvah to return the item, so long as it is intact, even if the owner subsequently abandoned hope (yei’ush) of retrieving it.”
“What if the thief sold or gave the item to a third party?” asked Mr. Goodman.
“This is called shinui reshus, change of possession,” answered Rabbi Dayan. “So long as the owner retained hope of retrieving his item, it remains his, and the third party is required to return it. Nonetheless, Chazal instituted a takanas hashuk, commercial enactment, that the owner, if he wants his item back, must compensate the third party whatever he paid in good faith, whether at value, more, or less.” (C.M. 356:2;8)
“What if the owner abandoned hope?” asked Mr. Meyer.
“If both factors are present – yei’ush and shinui reshus, the purchaser acquires ownership of the item,” replied Rabbi Dayan. “Since the owner severed his connection with the item and it was transferred from possession of the thief to a third party, he does not have to return it.”
“Does the order of these two factors make a difference?” asked Mr. Goodman.
“The Shulchan Aruch [C.M. 353:3, 356:3, 362:3] cites the Rambam that the order does not matter,” answered Rabbi Dayan. “However, the Rama rules like other Rishonim that yei’ush must come first. Shinui reshus is effective only after the owner abandoned hope of retrieving the item. Otherwise, the third party becomes responsible to return it. Most later authorities rule like the Rama.” (Shach 353:4; Pischei Choshen, Geneivah 2:)
“Mr. Goodman bought the coat in February, before Mr. Meyers abandoned hope,” concluded Rabbi Dayan. “Therefore, he must return it. Moreover, Rama rules that the practice is to return even after yei’ush and shinui reshus, in accordance with dina d’malchusa, civil law. Later authorities explain that halacha encourages doing so, anyway, lifnim mishuras hadin, and it became the common practice enacted among Jews. Nonetheless, Mr. Meyer must compensate Mr. Goodman whatever he paid, because of takanas hashuk.” (Rama 356:7; Shach 356:10; Pischei Choshen, Geneivah 3:21)