Well, Svalli mentioned the same thing happened with one variety this year - attributed to unusually hot conditions? Scroll down a few and you'll see her thread - fall planted hardneck producing single bulb or something to that effect.
So it could be caused by your temperatures this season, and that variety was sensitive and reacted by not maturing...
Incidentally, you can replant the single "rounds" that you got, if you want to give the variety a second chance, as long as they're not rotted.