The model for the blizzard "ice shard' is listed under the 'abilities' if you are looking through all of the game models.
For example when selecting the model you have Units, Doodads, Abilities, Buffs, Spawned Effects, Extras. The Ice Shard that the Blizzard Spell uses is somewhere in the 'Abilites' section I believe.
You could also just go to the Blizzard Spell and just copy it's Art- Effect.