I was in Baghdad back in 2007, and we definitely found some of that cash. Al Qaeda Iraq and Jaysh Al Mahdi were in possession of large amounts of it, and subsequently, so were quite a few of us lower-enlisted.
Lots of sweating and nervous glance in the customs line going home, and lots of subsequent purchases of fast cars when we got back. I only wish I wasn't such a pussy who was afraid to get caught back in the day.