Do you have the Collector's Edition? That sounds like the bow on sale at the elven fortress halfway between Arindale and Fargrove.
SWC
Sir Edmund:"Should you obey the lord who asks you to put a village of innocents to the torch? Is that chivalrous? Is it noble?" Me:"It's a great way to get promoted, I know that much."
If you're playing version 1.4, then the elven fortress won't be there, and you won't be able to buy the bow. But the bow will still be in the game. You'll just have to get lucky and find it in a chest.
SWC
Sir Edmund:"Should you obey the lord who asks you to put a village of innocents to the torch? Is that chivalrous? Is it noble?" Me:"It's a great way to get promoted, I know that much."