The flower buds were formed last year in late summer/early fall. There are several possible explanations for why one formed lots of buds and the other did not, including the possibility that the non-blooming one was, as you suggest, mislabeled. Next spring should provide the answer. Chances are, assuming no mislabeling was involved, both will bloom normally.

Thanks, akamainegrower. I have a lot of azaleas, including a dozen Encores, but I just love those little gumpos best. It broke my heart to see it sitting there without blooms when the other looked so sparkly. I will give it good care through the rest of the year, and trust that you are right.