So the rules say that magic items (including attended ones) get the better of their save or their holder.
Otherwise unattended items generally do not take damage or need to make a save unless otherwise stated or if the wearer rolls a 1.
If I case break on a non-magical bow currently wielded....the save is for the item. Does it use the save for the item (whatever that may be) or the fortitude save of the wielder?
Wielder, I think. Because the wielder is holding the item and would try to prevent the break.
Edit: Yep. Wielder's, if it's better.
"(object): The spell can be cast on objects, which receive saving throws only if they are magical or if they are attended (held, worn, grasped, or the like) by a creature resisting the spell, in which case the object uses the creature’s saving throw bonus unless its own bonus is greater. This notation does not mean that a spell can be cast only on objects. Some spells of this sort can be cast on creatures or objects. A magic item’s saving throw bonuses are each equal to 2 + 1/2 the item’s caster level."