When Blind Fury reveals Final Spark from opponent's deck but you have no runes to pay for the Deflect cost on opponent's only unit, what happens?

Ruling: You cannot play Final Spark through Deflect if you're unable to pay the Deflect cost.

Nuances:

• The rules are unclear whether Final Spark gets recycled or remains on top of the deck
• It's ambiguous whether "the rest" refers to all unchosen cards or all unplayed cards
• The comprehensive rules need updating on what happens when you're unable to pay costs for a spell