Leslies post reminded me of a similar incident I had. I bought a really cute dress at Dressbarn, and I must have left the store without realizing that the security tag had not been removed. Weeks later, I was getting ready to wear that dress out when I noticed the security tag was still attached. It was the kind that you can't remove without the special tool.
So, I took it back to (a different) Dressbarn and told the SA that I had bought it and they hadn't removed the security tag. The SA said that as a matter of policy, they wouldn't remove the tag unless I had the purchase receipt. I didn't have it. I told her where I had bought it and pleaded with her to remove the tag, but she still wouldn't.
Then I remembered the names of the two SAs who helped me with my purchases that day. The SA called up the store and confirmed with the manager that both SAs worked there, and she removed the security tag.