I seriously doubt it, and it would only be purchasing your pesos back if you had sold them via a legal, registered currency exchange/bank, it was properly logged with your passport, you retained the receipt, and I assume you had an even number of dollars for pay out in $100s.
If your plan was to sell dollars for pesos on Florida Street/WU and get dollars at Ezeiza that's definitely not happening.
This is likely an instance of de jure vs de facto, even if you follow every requirement and traded your dollars legally, you'd likely encounter every excuse as to why it's not possible to go the other way around. Sell your dollars as you need them, and with the remaining pesos buy snacks/drinks at the duty free/kioskos, they take split payments so you can even get rid of all your pesos in cash and pay the difference with a card.
