Take a look in your owner's manual under Tires, Wheels, and Loading. Granted, my truck is a 2010 but the tranny is the same.
Under Recreational Towing my manual specifically states that a 2WD truck CANNOT be flat towed. It must be towed with all four wheel off the ground. A 4WD can only be flat towed if it has a manual transfer case that can be put into neutral.
I understand the new electronic shift Xfer case on 2012's is different and can be placed in neutral for flat towing.
Looks like you're in the same boat as me, either look into some type of driveline disconnect or get a tow trailer.