You’re describing the crux of the “credit default swap” fiasco: “Half-trillion, half-trillion, who’s got the half-trillion?” SOMEBODY had the money, a LOT of it, loaned it out, and wants it back no matter how obfuscated the money trail got. “Can I borrow $10, but you only give me $5, so I owe you $5 and you owe me $5 so we’re even?” doesn’t work.