The ifrit fight and joining a GC really isn't that far into the game so it's not a terribly big burden, I got my riding license at lvl 22 and doing it solo. Yea, I couldn't ride my gobbue until then either. I'd double check the calamity salvager, the horn was at the very bottom of the list for mine. Worse comes to worse, I'd submit a GM ticket about it, it might just be in error.