I think this is possible and what i said about not getting maria from card broker might be wrong, I just noticed in my own heropedia that a lot o hereos which i have unlocked from royal arena but not recruited do not show up there. I know that players can also recruit heroes from the card broker as i have seen that in chat so that does suggest maria can be gotten from this card broker. This could be a glitch though like matt said or maybe thats how they want it idk.