Face-down Decoy Dragon?!?!

[Vampiric Omega]

This morning I saw a duel between a warrior deck and a BEWD deck. Warrior player throws out a "Blade Knight" and has no cards in his hand and no other cards on the field. Dragon kid has only a face-down monster, and Warrior attacks with no fear b/c "Blade" can negate flip effects. Warrior is suprised to see the face-down "Decoy Dragon" and even more suprised when Dragon kid slaps a BEWD on the field using "Decoy Dragon"'s effect.


Question: Is "Decoy Dragon" still able to get his effect if he is attacked face-down and flipped?

 

[skey23]

The rulings found for "Decoy Dragon" answer this question...

"Decoy Dragon" must be face-up at the time it is declared as the target of your opponent's attacking monster or its effect will not activate.

The play was not a legal play.