Yesterday evening I went downtown to the library. I had hoped Who's Who in American Art might have a listing for Jack Hearne, but no such luck. He's not listed in Illustrator in America or on AskART.com. At this point it seems that if not for Jim Amash's interview with Vic Dowd in Alter Ego, there'd simply be no clue to who Jack Hearne was.
Another detail from Dowd: Jack Hearne "was partially deaf in one ear, which probably kept him out of the service." Kind of ironic that the most extensive example I've found of Hearne's advertising art is this series of military illustrations for Douglas Aviation.