The LFS isn't 100% to blame. The vast majority of petstore owners rely on the knowledge of their staff and the credibility of the people whom they buy their wares off of. The true culprit is the company/salesman that is passing them off as aquatic plants.
That said however, if you tell the proprietor of your LFS that it's not aquatic, provide them with credible proof, and they continue to carry it as such, then yes, the blame is 100% on them.