so this is building management

My -iphone4s was stolen on last month.. i really feel upset on it.  It just with me for 3months.. The incident was happen like this.. ....

A stranger come to our office claim that he was a debtor.. So my colleague open the door & he stole my phone when noone notice on him. When i found my phone was lost immediately i check on building cctv & found that the stranger never register which suppose to do so for all visitor. 

From the cctv i saw the thieft was try so hard to access to our  floor since it was restricted. at that moment , no security was going to verify his identity. I wonder are there any1 monitoring on cctv. If not, why no people suspect on him. 

When I ask the building management why the stranger never register so that we can trace back his identity. But the answer is.. Maybe he follow the clowd go into the lift. So "common sense " will thought they are in gang. But they never give an answer on.. Why no people monitoring on the cctv & if got security monitoring on it.. Why don't have " common sense " suspect on the stranger when saw he try so many times to access to our floor . 

Building management never admit that they should responsible on the losses of security & when I want an apology report from them, their answer is need discuss with upper. & already 1 months they still not yet revert to me. is their working progress slow ? or This is the way they settle the case. DENY on wrong.. IGNORE complain. ACT usual like nothing happen.