Where is my sensor?

I did not originally install my system. Now I am getting a low battery alert for my garage glass break sensor. The problem is, I can only find my motion detector. I’ve looked on walls, ceiling and even behind things. There is an old aluminum sliding window and I’m seeing nothing there. HOW can I locate the sensor to replace the battery?

Please note that in Alarm.com it looks like the sensor you are referring to with a low battery is just named Garage Window, not Glass Break. In fact, its programming indicates it is a DW10-345. This would be found on a window frame.

In general and for other readers, sensor communication is one way, from senor to panel. There is no way to ping sensors so to speak with most systems. If you move into a location with a system you should definitely be sure to locate and test all sensors. It is also possible if you cannot locate the sensor in its logical spot that it was physically moved by a prior user but not renamed. You would want to test all sensors of that type to determine which is named incorrectly and rename.