Tristana's E removed by Alistar's Headbutt [Gameplay]

I haven't been able to reproduce this issue, but in one particular instance, Tristana's explosive charge was placed on Alistar, only to be left floating in midair and completely removed after Alistar used headbutt towards a wall after its placement. I am not sure if the headbutt needs to connect with another champion in this instance or if it was just a freak occurrence due to rapid timing, but I figured this was definitely worth mentioning.