Alistar Bug

I dont know if anyone else has experienced this, but while playing a game as I was against a and i noticed a pretty big bug. Whenever i did my W,Q combo. (headbutt, pulverize) If Sivir spell shielded at the right time she could negate the cc effects from both the headbutt and also the pulverize. Also the damage was completely negated. This only happened a few times, sometimes it would go through and the spell shield would work correctly, but 3/10 times it would block both skills. Anyone else notice this?