Fun Fact: May 9 is National Lost Sock Memorial Day in the United States. It’s a quirky day dedicated to recognizing the missing partner in a pair of socks and encourages people to say goodbye to mismatched socks and streamline their wardrobe.by johnataylor on TwosFun Fact: May 9 is National Lost Sock Memorial Day in the United States. It’s a quirky day dedicated to recognizing the missing partner in a pair of socks and encourages people to say goodbye to mismatched socks and streamline their wardrobe.