As far as I know, he only way to turn the alarm on is with the fob.

You can lock the doors from the door switch, and unlock the
drivers door with the key, but woouldn't you still have to unlock
the other doors with the inside door switch.

The alarm will only activate with the fob, right???

I think you may have seen some interference with the first
location, but did you try the first fob as soon as you got home???

 

The alarm is set also by using the switch on the doors.

This should sound the alarm.

 

The standard factory one?

 

I had this problem over the memorial day weekend. The battery was low in the HHR though. We went on a museum tour and both of the passengers left their laptops plugged into the power adapters. I cranked it and drove it a few hundred miles and everything went back to working normal.