Car Alarms: Subaru broken into, subaru outback, electronic key

Question
Over the weekend, my 2007 Subaru Outback was broken into but surprisingly
there was no broken window or broken lock. When I got to my car and saw
some of my things on the ground outside, I knew someone had gone into it
and when I went to open the door the alarm went off but the door was
unlocked. I'm 100% certain that I locked the car- I remember specifically
doing it. The thief/thieves took only my bag of clothing, leaving my ipod
curiously.  Is there a way to break into certain cars with some kind of
electronic key?  If I had left the car unlocked, the alarm would not have gone
off when I opened the door, right?

Answer
I'd go to Subaru for some clues as to why this is happening.
Your alarm frequency seems to be "too" common, and is picking
up someone else's signal, thus unlocking your doors too.
Not cool.

Call the service dept. to find out what you can do about it.

ALARMTEK