If the target creature is an illegal target by the time Hour of Glory resolves, the entire spell doesn't resolve. No player reveals their hand or exiles cards from it.
There are many important moments in the story, but the most crucial—called "story spotlights"—are shown on cards. These cards have the Planeswalker symbol in their text box; this symbol has no effect on gameplay. You can read more about these events in the official Magic fiction at http://www.mtgstory.com.