Elemental Hero Bubbleman was originally released in the "Structure Deck: Elemental Heroes" which came out in 2003. It wasn't reprinted in any of the packs released at the 2008 World Championship.
The 2008 World Championship used a different format and had different packs available. The prize packs given to the top players at the event included:
* "The Duelist Genesis"
* "Judgment of the Light"
* "Stardust Overdrive"
Therefore, while you could have won these packs at the 2008 World Championship, you wouldn't find Elemental Hero Bubbleman within them.