I don't generally get irked with people. But I had a similar deal at Auto Zone a while ago that severely tried my patience. I wanted a drain petcock for the radiator on my Valiant. Off I go, to enjoy the following exchange:
Clerk: How can I help you today?
Me: I need a radiator drain petcock in 1/4 NPT thread.
Clerk: What year, make, and model?
Me: It doesn't make any difference, it's a universal part.
Clerk: I have to have year, make, and model to look it up.
Me: (beginning to stew) It's a 66 Plymouth Valiant.
Clerk: Who makes a Plymouth?
Me: Plymouth makes a Plymouth. They don't make them any more.
Clerk: (searching) It says they don't make that part for your car.
Me: (stew factor ramping up) I know they didn't come with a petcock, just a drain plug. I want to add one.
Clerk: What is a petcock?
Me: It's a plug with a valve to drain the radiator.
Clerk: So you want a plug.
Me: (stewing along nicely) No, I want a drain petcock.
Clerk: Well I can't sell it to you, nobody makes that part for your car.
Me: (fully stewed now and very graciously not dragging this idiot over the counter to administer a richly deserved beating) - Walks out, goes to NAPA, tells the counter guy what I want and five minutes later leave with my petcock. Auto Zone sucks.
My GF tells me I should be gentle with the youngsters of today. In my mind, if you're going to work at the auto parts store, it would be intelligent to know something about autos and parts. Call me crazy, but that sounds like a good idea to me.