"I might be on the phone every time someone came in asking for AN. (And yes, some do wear cammos, more or less often depending on if they're doing some hunting after they put in the order for fertilizer.)"
No tan, no calluses on the hands, unfamiliarity with the product to the point of not knowing 10-10-10 from double ought six. My father grew up on a farm, all my neighbors growing up were farmers and I worked summers on those farms before I got my driver's license and "escaped," lol. There are obvious visual cues, and this guy would know them just as well, if not more so, than I do.
Whatever. Since you're the expert, let's just put it all on your shoulders. The facts are, this is farming country. Lots of farmers buy fertilizer. Some clerks in farm supply stores haven't worked there all their lives, and they hope they won't have to either, because it's a minimum wage job. You want to unload on a clerk, go ahead. You look like a bully, though. (It's not as though he sold him any of it anyway.)