Consider a card like Ashcloud Phoenix (or, for that matter, any card with a death triggers that's turned face down by an Ixidron).
When Ashcloud Phoenix dies, return it to the battlefield face down.
If I play my Phoenix face down as a morph creature, and it gets killed (say, by a Lightning Bolt), what happens next? Do I get to return it to the battlefield face down, or will it just stay dead in my graveyard?
- On the one hand, it was face down when it left the battlefield, and thus had no abilities.
- On the other hand, it enters my graveyard "face up."
So, does its graveyard trigger apply?