Did they ever zero them out? AFAIK they are still bookable, though if there is no award inventory available, you won’t see them listed.

I used DL miles back in 2016 to book on Aerolineas Argentinas from Buenos Aires to Ushuaia and back. One thing to note: the flight time changed at some point in the months between booking and travel, but DL never notified me. I rolled up to the airport in BsAs only to find out that the flight I’d been booked on had left an hour earlier. Luckily, the Aerolineas Argentinas check-in staff were nice enough to book me on a later flight that day (and luckily, there WAS a later flight that day). It could have been very problematic, since I was flying to Ushuaia to get on an Antarctic cruise that left the next day.