Current price of crude oil per barrel: 68.48
http://www.bloomberg.com/energy/
Using the the LOW estimate of the war costing 1 Trillion Dollars we have the following: $1,000,000,000,000 / $68.48 = ~$14,602,803,738
So using the low projected cost of the Iraqi War, the same spending dollars wise could buy more than 14.5 billion barrels of oil at today's prices on the open market.
How long would it take for Iraq to produce 14.5 billion barrels of oil at it's maxium pre gulf war 1 rate? Well, 14,602,803,738 / 3,500,000 = ~4172 days. That's more than 11 years.
Conclusion: Under ideal conditions, it would take Iraq more than 11 years to produce enough oil to offset the overall cost of the war. Assuming that the US just took the oil and didn't buy it.
Maybe your deffinition of stealing is different than mine?