The real black market is the hidden one, the one where millions are moved every day. Just because members of government banned currency exchange doesn't means they and their friends can't buy dollars or other foreign currency, and they do, sometimes subsidized by the government given that they buy at the official rate which is near half that of the real market rate.
The only thing keeping this disaster from graduating to hyperinflation is the fact that for the first time in 100 years Argentine exports are back in high demand, back then it was the British and French, now is the Chinese and Indians buying Argentine food products. That source of foreign currency feeds the vaults of the central bank allowing the current government to keep this Jenga-economy from falling apart, let alone stuff their pockets.
Ironically 100 years ago Argentina used that money to build its industry, fund the arts, providing top-level education to the population and build its infrastructure, all with the best of the best. Today this new money is being squandered by a government so corrupt it dwarfs even the worst of the early 20th century Argentine elite. The irony is that Argentina is building nothing today, in fact most of the country still lives everyday using the (now decrepit due to age and lack of maintenance) infrastructure created in those days (or with the wealth from those days) meaning this time it will not only repeat the same mistake of depending too much on primary exports but it will leave nothing for future generations.