[Gameplay] Alistar W+Q Combo not applying Q but still putting it on cooldown.

This happened to me several times my past 2 games. When doing the patented Alistar W+Q Combo, both skills would end up on cooldown, but no Q (Pulverize) was cast. This leads to the opponent flying away harmlessly instead of getting CC'd for your team. Not sure the actual cause, but my only thoughts would be that I might have spammed my Q button. The enemies did not have any sort of CC that could interrupt it, and no animation of smashing the ground was done.