There is one episode where Quentin's 1930s/40s pre-Grant Douglas identity is mentioned. Julia finds a clipping and some other things and a name is mentioned. I can't recall it at the moment but it's one of my favorite episodes. I love the shows where Julia is trying to help "Grant" overcome his amnesia just because I think Grayson and Selby had such fabulous on-screen chem.
But you're right, the show could have done more with this, but they didn't. An option might have been to have a storyline that involved the 1920s and Quentin having to do the I Ching back to his former self then and come to Collinsport and change history. I think Selby would have looked very hot in 20s regalia, and the women would have looked great in the period fashions too.
Ah, we can dream...
G.