The shliach Chabad in one of the neighborhoods of Beer Sheva lost an earing. The daughter was playing with the earing and stuffed it into the couch. 

When the parents, Rabbi Mendy and Gitty Yitzchaki, were looking for the earing among the cushions they instead found a bunch of enveloped stuffed with money.

They were gifted the couch by the previous resident, the owner of the apartment when she left for the old age home. She was an older Russian woman who only spoke Russian and Yiddish.

So they found these envelopes stuffed into the couch - enveloped filled with dollars and euro to the tune of 100,000nis.

They tried to talk to the woman in the old age home to tell her about the money they found and return it to here, but she had no idea what they wanted from her. She didn't remember anything about the money. So they contacted her son, a doctor, instead. After telling him what happened,, he came to pick up the money, leaving a $300 donation to the Chabad house, and agreeing to put on tefillin.

They never even found the missing earring.

sources: Behadrei, Haredim10

halachically I wonder if they even needed to return it. While found cash does not normally need to be returned, this is cash in envelopes stuffed into a couch, so it would be as the way it was hidden is considered a siman. However, the person they think who it belongs to has no memory of it and did not claim it. They gave it to the son who had no prior knowledge of it. Maybe the woman got the couch from someone before her and the money was not hers either!

Whether they needed to or not, they made a nice kiddush hashem by giving up what they could have kept without telling anyone. As they said, we were gifted a couch, not envelopes of money, so it isn't ours.