When Ennis calls Lureen to find out about Jack's death, she says, "Jack used to mention you, you're the fishin buddy, or the huntin buddy, I know that." A moment later, she says, "Would a let you know what happened, but I wasn't sure about your name or address."
So which is it, she knows his name or she doesn't know his name? And we know she knows what state he lives in, because Jack would go up there "two, three times a year." She could have found him, I bet. At least she could have tried.