How does Ethan know Cameron's last name from somewhere and what does he do with the information?

Ethan has heard Cameron's last name--Cassmore--from somewhere before. Then he remembers that when he bought the Shop-Way, the old owner posted bad checks from customers tacked on the counter under the cash register. One of the checks was from Daphne Cassmore. He looks her up on an ancestry website he belongs to and learns that she later married and became Daphne Scott. Then he finds information about her half-sister, Jeanne Baker. He realizes that Daphne is Cameron's mother.