Lots of people buy the vests. They are very popular among "prepper" types. Thing is normal people (especially those texting on cell phones) typically do a fair amount of research before purchasing one and this guy seemed fairly clueless, that and a request for bulk ammo would seem very odd.
One would think since he had worked in security for so long he would already know where to buy vests and the like, or at least know to call ahead and find out who carries them, but he didn't. I have been to enough local gun stores to know that they don't typically carry vests, but he didn't know that because he doesn't have much experience.