Sounds dumb, but it could be a disconnected vacuum hose near the fire wall. The hose will be a small in diameter,btw. I saw it happen twice to newer trucks at work. The air hose controls a flapper that changes the heating/cooling system with the dial on the middle dash. If the hose is disconnected, it stays in cooling mode. Other wise it would have to be a heater core, if your car is warm and your air is not. Do you still have a warranty? If yes...get them to check and hopefully fix it under warranty.
Edit: Btw, the lower and higher coolant hoses are going to be different temps. One is a return hose and one is a feed/supply hose. The upper hose carries hot coolant (a mixture of water and antifreeze) from the engine to the radiator to be cooled. The lower hose brings coolant that has been cooled in the radiator to the engine.
378awhp/373wtq Custom Dom 3 & CBRD tuned 2006 STI.
"When in doubt...flat out" - Colin McRae