Recall channel bar not disappearing when taking damage

I was channeling my Recall when I took damage and the spell was interrupted. However, the progress bar didn't disappear. It continued to go down until it emptied, at which point it disappeared and nothing happened. I was playing Morgana and I believe the attack that hit me was Fiddlesticks's Dark Wind, though I'm not entirely certain. Other enemy champs were Sion, Leona, Veigar and Kalista.