I was always under the impression he was abducted from his home in NY and sent back. At least, that was the story told in Theramin, An Electronic Odyssey.
 - https://www.youtube.com/watch?v=fAOpVAHwLic
Perhaps a whole bunch of electronic warfare devices like those used against AEGIS and the USS Donald Cook? And what about the fact that NASA and the US space program are so dependent on Russian rocket engines? Or the Russian jet that can hover or reverse in mid flight?
We know that the Russian system of higher education is very rigourous and places a lot of emphasis on mathematics Could this be the root of it? Or is it something else in the culture of Russia?
One of the biggest mistakes of the USA after the Cold War was to stop taking Russia seriously and to stop watching what Russians were doing. The west accepted the views put forward by Ukrainians about Russia, instead of going direct to the source. Now we know that neo-nazi forces within Ukraine were spreading misinformation about Russia in order to benefit Ukrainian oligarchs.
It is time to move beyond this. More of us need to learn Russian fluently and analyze Russia based on direct knowledge of the country and people. Russia isa powerful nation and it has a rich and vibrant culture. There is a lot to learn there, not just about technology but also about how to approach and solve impossible problems.
And also a wonderful illustration of political machinations, in that the olive branch extended to you often has a covert team watching exactly how your fingers grasp it.
Current bug detectors explicitly detect non-linear elements. A hilarious practical joke involves adding diodes to the concrete mix for a high security facility. Back in the cold war the Russians actually did this to the Americans in Moscow.