I would suggest that the issue is not international relations, but that these two do not have any official capacity. It is hard enough to get an official respon

I would suggest that the issue is not international relations, but that these two do not have any official capacity. It is hard enough to get an official response to an official enquiry. Imagine you are the secretary at the Bolivian Embassy. Your job is to answer phones and direct queries about visa applications. You get a call from random people saying they have the flight recorder from a plane crash. You know nothing about the plane crash (it happened ~35 years ago) let alone the rules governing investigations. Best case scenario, you take the caller's details and forward it to your supervisor who is equally ignorant and has his real work to do . . . the call is forgotten, no response comes. This sort of scenario will play out in all government departments in all countries. Until the right person on one side or the other gets interested, nothing will happen. Unfortunately, the right people tend to be very busy and have probably not even heard about this development. Even if/when they do, it is a bit of a toss up how much they'll care. This is a really old plane crash, and the investigation has been closed.