CCW at work, not in handbook

Need some advice. I work at a drug and alcohol rehab facility (an 85 acre piece of land in Texas) and have been told by my employer that guns are not allowed on the property. This was only a verbal communication...nowhere in the employee handbook does it say anything about weapons on the property. I know Texas law says I can keep a gun in my vehicle since it’s private property but is verbal communication an effective means in Texas? I don’t plan on carrying at work, I just want to know if I need to tell them to update the employee handbook and also be able to argue my point if the issue ever comes up. via /r/CCW http://ift.tt/2wFyXD1