Do you still need help? Just in case, I will try to help you anyway. I think I got the same problem as you and this is what the developer told me:
"Strange. He's only available in Open Mode for starters. If he doesn't come up as a potential recruit, you may need to re-watch his final Story Mode scene to trigger the unlock again. There's also the cheat code "let's date" (F1 key by default) that you can use to unlock all the unlockables romances."
I think it is a bug or something. I recommend the cheat code because it is an instant fix. Have fun playing!