I had a 2008 DC w/Tow Package and I remember the tranny cooler off to the side. I thought the same thing when I looked at my 2010 DC w/Tow Package and wondered where it was.
Here is a shot of the front of the truck (2010 w/Tow)
What I am thinking is that they moved the tranny cooler directly in front of the Radiator... (and made it bigger) could be off on this, but I don't have a non-tow package truck to compare to. Look at the pic below and you'll see a thinner, black radiator in front of the larger, primary silver radiator. I think it is just beefed up and looks like one unit now.
Lastly, here is a pick from another forum that shows the previous style. Note the primary silver radiator does not have a thinner black one in front - obvious to see that the thinner black one is the tranny cooler off to the side.