Fiora Ulti disappeared

I don't have a link, but I play Fiora a decent amount and this has never happened to me. I ultimated a fizz, and quickly got 3 of the vitals procced. However, when I went for the fourth it wasn't there to hit, but I know I didn't get the heal buff for hitting all four either (my jg died as I got the first 3 procs.) I don't know if it was a one time thing or if other people have experienced it, but just putting it out there.

TLDR: Fiora ult ended early/disappeared