I'm constantly surprised by what bike shop salespeople and even mechanics do not know and will not admit to not knowing (what is possible as far as drivetrain compatilbity, what Shimano shifter parts you can in fact buy new individually, etc...). The flipside of this is that a great many of them would also know a great deal more than those that are not employed in the bike industry at some level (as a result of their job). I think part of this phenomenon is that many (notice that I'm not saying all) full time bike mechanics would rather not spend their free time on places like BikeForums finding out obscure bits of bike related knowledge when they spend most of their day dealing with the routine. A big part of why we regularly experience this kind of thing is that we often tend to encounter the salespeople first, who might not be as knowledgable as the mechanics who are in back working. I live in a portion of San Francisco that has at least five bike shops within about 10 square blocks - I've been shocked at the variety of answers I've recieved from each shop over the same questions time and time again (not that I haven't been relatively pleased with the service I've received anyway).
I guess what it boils down to is that people who work in bike shops (sales or mechanics) are just people too, many of them are pretty darn smart, many are probably complete idiots who try to hide that fact, many, like you or me, are just trying to get through another day of work (but they probably don't have Internet access to waste time on BikeForums). Either way, I sympathize, finding chainring bolts shouldn't be nearly that hard.