While that is a fair assumption, we are all making assumptions on this persons behavior, the clerk, and the officer. Just because something is unlikely in your mind, or mine, does not mean it is unlikely in the mind of the clerk or the officer. How long was this person in the store? Was it long enough to make the clerk nervious, or feel that he wasn't just there to buy a drink? Again, without the call it's speculation as to why the officer was requested.