A couple of years ago, I saw hostas at Lowes that had definite signs of hosta virus X. I told the garden manager there, and they pulled and returned the entire shipment. All of them! I saw hostas at our biggest locally owned nursery, same situation, and they argued with me. Told me that it was a rare disease, not found in our area, and there was no way I could tell from looking that the virus was on their plants. I brought them a handout that I use in talks and they still didn't budge. they kept selling the diseased plants.
The big box stores have experts they can call, and have deals with their suppliers where they can return unacceptable plants. The locally owned stores rely on in-house "experts" for the most part, and most of them really can't take the financial hit of destroying a whole group of plants. In a perfect world, they would have called on someone at the extension and would have confirmed what i observed, but I think they underestimated the seriousness of the disease.
Or maybe they underestimated the passion of local gardeners, because as others saw the same thing, word got around. It cost them a lot more in the long run.