After talking with a contact I was informed that there is in fact a fully functional alarm system in this gem of a historic space. The motion sensor was placed there after scrappers infiltrated the space, and scrapped electrical cables that were feeding power to the surrounding, active buildings. I am still confused as to why it took so long to go off. We walked by it many times, even stood right in front of it. I was left to believe that it was on a timer of some sort. But I have never heard of such a thing.
This is the only image of the interior that I have. My card happened to corrupt on me that day. There was no chance at rescuing images, I tried. I am now working on trying to gain legal access to the site. The space still has some of the original equipment in it, lathes, etc.