I'm 22 and live in Huntersville (Mecklemburg County) and I haven't got my glock 19 yet, but this is what I would have done, cuz I'm going to OC in a couple of weeks.
When he said it is company policy, politely inquire as to why it was not posted on the doors. Also if he says it's in the handbook, and you are feeling bold and patriotic, ask to see the book. if it is truly company policy, apologize and don't bring your gun in, (or just CC ). If you are like me and new to OC, and he says it's in the policy book, you might just say, "Oh, well I didn't see it posted on the doors so I assumed it was OK." Then leave and let the Vet. OCer's handle that store to blaze the trail for us newbies!