Tangentially,

CIA and IB (Indian Intelligence) lost such Plutonium RTG powered listening device at a Himalayan peak in 1965 used for SIGINT against China. Further expeditions to retrieve the device resulted in failure and later they installed another such device in 1967[1] which was supposedly taken out in 1968.

[1]https://www.livemint.com/Leisure/3QfYqLadggrbnrn41H0mAJ/The-...