Aerolineas only honored the tickets in very specific situations - if you were already in transit by Thursday, and were coming home by today at the latest, then Aerolineas would honor the Pluna ticket, but only for this three day window.
I had a Pluna flight to leave on Saturday morning and got totally screwed by Pluna closing - I didn't get to meet my husband in Rio for a quick vacation while he is working. Well, I didn't want to buy a last min ticket for $800 USD. He has to buy a new ticket to come home, as he doesn't come back until next week and Aerolineas won't cover him.
No one was at the Pluna office or at the airport here on Friday, all the employees abandoned ship! All you could do was call the BA number, but they were completely inept over the phone.