As the one-sentence replies suggest, it's really a question of what type of game you're playing.
If you're playing a loose, videogame RPG-style game then just ignore the question. All inventory exists in some kind of undefined "backpack"--it effectively disappears when not in use. I see these gamers all the time. When I ask them where they put their glaive (or tower shield!) when it's not actively held, they just give me a blank expression and reply "Uh... in my backpack."
Yeah. A 10' pole with a 12" butcher's cleaver on the end. Stored "in" the (nonmagical!) backpack of your 4' dwarf. Right.
If that's the kind of game you're playing, just ignore the question the same way you most likely ignore food, watches, ammunition, familiars, encumberance, wand charges, light sources, and spell components.
If you're more into "realism", then work out some reasonable method with your DM. A decent "get on with the game" compromise is slinging a strung longbow over your shoulder or stuffing a shortbow in a quiver/case. Or drop the thing. Or use a magical solution, like a Quiver of Ehlonna or Haversack. Or hold it in your off-hand.
If you're really into realism, consider circumstance penalties to attack, AC, tumble, or all of the above if you choose to sling or hold onto that big bow. Give attackers circumstance bonuses to sunder attempts, or rule that an attack that misses by 1 point hits the bow instead.
From a strict rules perspective the bow is treated more like the first scenario. It simply adds to a vague "encumberance" total, and that's that. So it's totally up to you to determine the level of realism in your game. Find something you and your players are comfortable with, and run with it.
-z