The effect of the card says the following:

■ Whenever this creature attacks, you may reveal the top card of your deck. If that card is a non-evolution Dragon, you may put it into the battle zone.

But what, if the card is not a dragon? Put it back on top, on the bottom or to the graveyard? I think the card lacks translation.

The similar card "Magmadragon Balga Geyser" instead has the same effect, but has the wording "if it's not a dragon, put that card into your graveyard "

That part of the effect only appears on Balga Geyser.

The "Balga" family work in a similar way, but the effect does change slightly, even if they are all "drama" creatures. Even just to quickly google translate it, to give you the rough version...

http://duelmasters.wikia.com/wiki/Magmadragon_Balga_Geyser

このクリーチャーが攻撃する時、自分の山札の上から1枚目をすべてのプレイヤーに見せてもよい。そのカードがドラゴンであればバトルゾーンに出し、ドラゴンでなければ自分の墓地に置く。

"When this creature attacks, you may show all players the top card of your deck. If that card is a dragon, put it in the battle zone and if it is not a dragon put it in your graveyard."

http://duelmasters.wikia.com/wiki/Balga_Raiser%2C_the_Dragonic_Meteor

このクリーチャーが攻撃する時、自分の山札の上から1枚目を表向きにする。そのカードが進化以外のドラゴンであれば、バトルゾーンに出してもよい。

"When this creature attacks, turn the first piece of the deck from the top of your deck. If that card is a dragon other than evolution, you may put it in the battle zone."

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The revealed card just goes back on the top of the deck if its not a dragon.

This is true for http://duelmasters.wikia.com/wiki/Codename_Balga_Ragon as well.

Balga Geyser and Raizou put them into the graveyard explicitly. The Raiser and Ragon just reveal them, and then put them back if non-dragon.