Reading Hoover's page on their Chocolate Orpingtons, they apparently are breeding them as sexlinks, Chocolate male over Black female adults to make Black male and Chocolate female chicks, in which case I'm wondering if you somehow ended up with a male chick from those parents instead of a female. Your chick does have a rather large comb for a two week old Orpington... That would mean that he carries Chocolate, but it being a recessive gene, it's not expressed and he is visually Black instead. Your chick is Black either way, not Chocolate.