Since you say you are parts savvy, then it seems that your local NAPA has some software quirks (not unheard of). Regardless of such a situation, you still walk into a parts store "unarmed"?
Apologies... not to imply anything, or to seem "pushy", but do you leave "things" in the hands of others? I'm a parts guy, so I never rely on others--been burned too many times. It is always best to do your own leg work. Never assume the other person knows what they are doing (Like everyone else, I too am fallible--I make mistakes as well--this includes the computer cataloging). Doing your own research is always the best policy.
Again, with respect--I don't wish to come off in a bad light: I just want to communicate my experiences and be helpful.
I was in the store to get a different specific part and had a thought...."Hey, I should get one of these too"
The spur of the moment part was the T5 tailshaft seal and I figured NAPA will have that info in the computer.
I found out different.
Concerning "arming" myself before going to the parts store....That has become standard fare over the last 15 or so years.
While I hope the parts store will have what I need on hand, I understand when they don't because I am usually seeking parts for 50+ year old cars.
Because of this I try real hard to have a few brand names and part numbers with me, as well as industry descriptions, to help me attain parts as I assist the counter help in searching in the right area of the computer to find the parts.
But sometimes the parts search is spur of the moment, like it was this time.
I am not going home to do all kinds of research to then return to the store to look up a part.
When I am literally at the store, speaking with the help, looking up other parts, it seems reasonable to ask the help at that time to look up a relatively common part such as an output seal for a T5 that was so common without being armed and ready to assist the counter help in that search.....I found out I was wrong and moved on at that time.
I also found out, during my assist to the counter help, the NAPA computer does not even list the T5 as an option for ANY Fox body Mustang, and this struck me as odd based on the sheer numbers of Fox body Mustangs using a T5.
In my opinion this option, on this make, for this model having zero presence in the computer is simply wrong because it is such a common part on a common car.....Literally millions of them out there.
Anyway, like I have already said, this rant revolves around the total lack of any T5 option in the NAPA computer under any Fox body Mustang being weird to me.
It is not about how to navigate the parts store computers, where to look up parts, how to look up parts, or any other helpful suggestion within that realm.
Knowing things like how to find a heavy duty water pump for an FE by using a 1974 F350 truck with a 360 engine options as the reference vehicle so the counter help can "find" it in their computer is great......But I don't think a customer should have to provide special assistance help to the staff so they can find something as common as a T5 in a Mustang as an option in the computer.