I have close second hand knowledge of this. As far as I know, while misappropriation of all kinds, from sketchy to outright theft, was rampant and often condoned (e.g., at Brezhnev times), secret information was a different kettle of fish: losing it was not taken lightly.
The thing with information is that when things go missing, it's obvious, so people have no choice but to act on it. Still there must have been coverups, depending on how sensitive the information was, and how well connected the affected people were. It's unlikely that a system endemic with criminal activity would suddenly treat one specific aspect with a level of care that's not applied anywhere else.
Anyway, this story is about stealing a missile. I have absolutely no doubt the same thing could have happened east of Iron Curtain as well.
