I think these audits are just routine charades they carry out now and again to make it look as though the Pentagon's spending is being monitored, when in reality the Defense Department basically gets a blank check year after year.
I also don't buy the idea that they don't know where this money is disappearing to; black projects and black sites probably account for the vast bulk of supposedly "missing" trillions.
They know what they're spending the taxpayer's dollars on - they just don't feel like revealing their real expenditures to the public.
You're definitely right that people should be outraged that the military consumes so much of the discretionary budget, but I get the feeling a lot of Americans are afraid of what might happen if they try to scale down the US military at all.
It costs a lot to stay at the top of the totem pole, and most Americans seem to have come to terms with that fact.