Russia has actually been relatively honest about this kind of stuff from the 1990s and onwards. At least towards my country, the USSR was not very dishonest or plotting, and when ex Soviet military people were able to speak off the record without any risk of reprimands, they confirmed the officia USSR version of events, and digging around in archives that were opened up, again confirmed the USSRs version. Sweden had some issues with the USSR about a some missing people, submarines and a small plane that was shot down. Even though the assumption was always that the USSR was lying and covering things up, as it turned out,they had been telling the truth, more or less, including when it was not particularly flattering on them. Actually, our own polititicians and media had been MORE dishonest than the USSR, simply lying about what the military, and individuals had been up to, on Soviet territory.

I honestly think this is a fanciful story that probably doesn't have a lot of substance although undoubtedly dramatic and intriguing.

Any kids that had survived something like this would surely remember it and look into it as adults. Any surviving adults would surely have spoken up by now.