Thanks for your reply. He's Argentine, so paid in pesos and Delta received pesos. In my mind, the question is what happened after that on the Delta end. I like to think they're smarter than to hold any funds in pesos, but perhaps they're legally required to keep in pesos. Just a guess.

One clue might be that his eVoucher amount as we kept trying to reschedule his return home (each return flight successively cancelled by Delta) was always quoted in pesos, about 70,000... Which brings up another question - does the eVoucher amount reflect the complete RT value or just the unused portion?