This weekend was the first time it got decently cold (mid teens) since I've had my 09 HHR SS. Anywho, while the car was running I stopped and got out to check something and was unable to get back in the car. Even though the driver side locking post was in the unlock position. Had to call a unlocking service to get me in. Is this a common problem with HHR's? Thanks

 

Common. Don't think so since I don't recall hearing of that same scenario.
Would be nice to know "how" the service actually unlocked the door. Via pulling on the unlock mechanism or using the lock cylinder.
Your description of the lock knob appearing to be in the unlocked position could be 2 different things.
Either the lock knob rod has come loose and the door was actually locked. Or, the rod is still attached and the lock mechanism has failed internally even though the rod was up.
Either way, I would suggest pulling the door panel(easy job) and taking a look. Even if you don't see any obvious problem, might be best to replace the assembly so it doesn't lock you out again.

 

If your battery is the OEM original, it might be time to have it load tested, or simply replace it. A weak battery wreaks havoc with the HHR electricals .
Mine showed 12.5 volts and still failed , turned out it was to weak . A dead or dying cell.

 

It might not be a bad idea to have a spare key hidden and accessible from the outside.

You might be able to keep one in your wallet or.....

Silverfox

 

Here how it happened.
1. Pressed the unlock once on the fob to get in. I realize pressing it twice wouldve unlocked all doors and I wouldnt have had this issue.
2. Started Car
3. Got out of car to check and closed the car door to make sure i locked the house
4. Couldnt get back in car

 

Does not seem to have anything to do with the electronics.

If it was locked you could not have got out of the car.

A mechanical problem in the latch is my guess. Not locked, but stuck. Or the door handle to latch connection.