I was a member of the 25th Infantry from 1978 until 1981. They had the US Army’s record for most lost weapons.
My unit was “fighting” against a Marine unit. The Marines attacked another unit not involved in our training and a brand new Army private panicked and dropped his M16. A Marine stole it, hid it and returned later to get it. The police found the M16 about 6 months later during a raid on a drug house. Yes, it had been traded for drugs.
The amount of theft from the military is huge. Computers, weapons, ammo, money. For a long time, stolen ACOG and EOTECH optics were being sold all over the internet, as they were easy for people to slip in their pocket. With the current price of ammo, I bet the rate of theft is pretty high.
Of course, this is all petty theft, and pales in comparison to the theft by contractors.