Parts not on display in store.

Last week I went to the store in New Braunfels, TX to Buy 2 roof top vents for my fifth wheel trailer. The first time I went was on Sunday and the clerk knew what I wanted but they were in the service dept. shop and not available for me to purchase. I returned the next day and after speaking to 3 clerks, the vent covers were brought to me from service. This same situation happened to me about 4 years ago, the vents were brought in to me from outside in service.
My question is why not stock this merchandise in the store for resale? Undoubtedly there are other items that could be displayed in the store for resale as well.
Vents in question are...7" plastic W/base, retail $15.00 each.

Thanks for your consideration.