Does Feather, the Redeemed return an instant that targeted a creature you controlled even if that creature is no longer on the battlefield?

Feather, the Redeemed reads: 'Whenever you cast an instant or sorcery spell that targets a creature you control, exile that spell as it resolves. If you do, return it to your hand at the beginning of the next end step.' The trigger condition is checked at the moment you cast the spell — at that point the creature is on the battlefield and is a legal target (CR 601.2c, CR 603.3).

A delayed triggered ability is created when the spell resolves and exiles itself. That delayed trigger will return the card to your hand at the next end step regardless of what happens to the original target creature afterward (CR 603.7). The creature leaving the battlefield between casting and resolution — or even during resolution — does not retroactively invalidate the trigger that was already set up.

However, if the creature is no longer on the battlefield when the spell tries to resolve, the spell may have no legal targets and could be countered by the rules (CR 608.2b). If the spell is countered this way, it goes to the graveyard, Feather's replacement effect never applies, and the card is NOT returned to your hand.

Concrete example: You cast Defiant Strike targeting your Grizzly Bears. In response, your opponent destroys Grizzly Bears. Defiant Strike now has no legal targets and is countered by rule 608.2b — it goes to the graveyard, not exile, so Feather does NOT return it. But if Grizzly Bears died after Defiant Strike resolved and was exiled by Feather's effect, the delayed trigger would still fire at end step and return Defiant Strike to your hand.

So the outcome depends on when the creature leaves: if it leaves before the spell resolves and there are no other valid targets, the spell is countered and Feather cannot return it; if it leaves after resolution, Feather's delayed trigger still returns the spell normally.