Pre-Owned'04 X3 Alarm - do I really have one?

[odie3]

So, it seems that my X3 has an Alarm but when I use the key to lock it I do not see light blink or siren beep.

The only thing I am going on is the Rear View Mirror - it has a little red light thingy. From what I understand this is part of the Alarm System and show "blink" after locking the doors [which it does not do].

What might I check to ensure I do have a Factory Alarm and if I do where to start to find out why it's not enabling?

Also, there is what looks like a photo cell sensors on the front of the mirror [faces out of the front of the car] and one on the mirror [faces out to the rear of the car]. What are these? Also part of the Alarm Sensors?