Mom's safety compromised in secured alzheimer's/dimentia unit

Yesterday I went to the nursing home a little later than normal in the morning to visit my Mom.  As soon as I walked in one of the residents on the assisted living floor that Mom used to live on told me she found my Mom coming out of the door to the stairwell to the second floor wandering and upset looking for her babies again.  Mom lives on the 3rd floor which is the alzheimer's/dimentia unit.  This resident has been friends with my Mom for two years and is quite reliable.  She told me she immediately found a staff member and went on the elevator to return Mom to her apartment. 

I questioned staff and asked how my Mom could have opened the stairwell door and walked down a very steep flight of steps to the second floor.  I was told that she did this twice that morning.  I went to the stairwell door myself and pushed on the bar to open it.  An alarm immediately responded and 15 seconds later the door opened.  The staff not only should hear this alarm but their beepers are paged when this alarm sounds.  No one must have responded twice as my Mom did this!!! 

My Mom has fallen numerous times now and is definately unstable and a huge fall risk.  I have put a wonderguard on her wrist so that she cannot leave the building but apparently due to fire code this wonderguard will not lock the third floor stairwell door as it does the doors leading outside on the 1st floor. 

I plan to go to the acting director of the facility today and file a report.  I do not want my Mother to be injured or die falling down a flight of steps.  I have taken every possible measure I can to provide for my Mom's safety but this is beyond my control.  I was told by the head RN that the stairwell door cannot be locked at all times because of fire code but my husband works in the building industry and told me this is not true.  The doors can be locked at all times and if there is a fire alarm set to open then. 

I am beside myself with worry that Mom will do this again and her safety and health is now compromised.