That is right, though I cannot confirm your number.  The latest of relevance I could find was this (from January):

Audit: U.S. lost track of $9 billion in Iraq funds
Pentagon, Bremer dispute inspector general's report

WASHINGTON (CNN) -- Nearly $9 billion of money spent on Iraqi reconstruction is unaccounted for because of inefficiencies and bad management, according to a watchdog report published Sunday.
An inspector general's report said the U.S.-led administration that ran Iraq until June 2004 is unable to account for the funds.

But there may be fresher info out there (beyond my googling-capacities, which are quite limited).  I know I have seen more recent reports, but cannot recall the figures or find the articles.

Given the chaos under the CPA, I find it likely that most of the losses were due to embezzlement.  Pure and simple.