Well, there's about 80 or 90 billion dollars worth of stuff we abandoned in Afghanistan . . .
More seriously, some stuff is pilfered of course (sometimes by general officers) but most of it is probably paperwork. I've seen this sort of thing (on a MUCH smaller scale, of course) in a big corporation - someone who's been diligent in documenting stuff retires, quits, or is laid off, and nobody is assigned to fill the now empty slot - in fact, often the slot itself is eliminated. And a year or two later there's some kind of audit - assets, regulatory, safety, whatever - and suddenly the paperwork isn't there. Since the top brass assigned NOBODY to do the work, and NOBODY gets credit for doing "non value added" paperwork they weren't assigned, the paperwork didn't get done.
BUT THEY NEED IT!! NOW!!!
Much hilarity ensues.