Wirelessly posted (Palm Pre: Mozilla/5.0 (webOS/1.3.1; U; en-US) AppleWebKit/525.27.1 (KHTML, like Gecko) Version/1.0 Safari/525.27.1 Pre/1.0)
I doubt they are operating without a license. It's probably one (or more) of 3 reasons you can't find the license.
1. They use a private security company and the frequency is licensed to that company.
2. The frequency is licensed to the company that owns the mall. The name of that company may not stand out as being a mall.
3. They are using a private radio service where they pay for usage of the radios. In this case, the frequency would be licensed to the company that owns the radios. There are several of these companies in the area, the most well known is probably Ancom.