I have reached Yuki nirvana
I had the exact same thing happen 2 weeks ago on Fena.Right.... Now I feel very silly. Haha.. :$ I kept picturing that somehow the song's vocal would be in Wakana's voice for some reason. :")
Even worse, turned out I had heard the ?original song some 10minutes prior to the BGM in the opening of the show... I was convinced it was an old FJ/Kalafina song. How embarassing.