I'm fairly sure that the reward for "Fowl Thief" is not set at all...

There, I just checked, and the Mission Prize FAQ on GameFAQs.com agrees with me. The reward is any two of the following items:

Burglar Sword
Atmos Blade
Barong
Falchion
Kris Knife
Silver Rapier
Ninja Knife
Pure Staff
Firewheel Rod
Thunder Rod
Char Bow
Conch Shell
Kaiser Knuckles
Ice Shield
Wizard Hat
Blaze Robe
Battle Boots
Javelin
Buster Sword
Fortune Ring

So you are probably thinking of a different mission...