I think they were too conservative--a 55 to 58 made more sense to me, given the really nice surfaces, and eye appeal--but it was a wash. Should definitely get a green bean, as it is a really attractive coin, and not that commonly seen in that condition.
Tough result, as usual hindsight is perfect, keep in the fatty NGC holder get the CAC sticker and market. You could always try more submissions, like many dealers do with coins that can grade in a good range on any given day.