Again, the point was that a war fund isn't just a massive account full of money. Do you think DARPA just goes out every few years and says "Well, I'm gonna drop several dozen trillion dollars into X or Y project and we're gonna be super-badass afterwards!"? (well, yes, but welcome to the American debt >_>). No, we have industries that produce many of the higher-cost things that would otherwise drive prices up the roof, and we spend in proportioned, progressive chunks. Tax revenue, trade, etc, slowly cover the rest of the going costs.
So in essence you can't steal what wasn't there. But I digress... a billion is a lot more reasonable. That's the cost of a couple ISDs IIRC (may be a bit off), so to have something like that at the ready in case one is lost in a major naval op is far from unbelievable. Money like that still doesn't go unnoticed though.