I recently got a bug report from a rather discouraged archer, who was trying
over and over to fire a longbow while a non-weapon called 'arrow' was in his
inventory. This item was a silly little random piece of trash the archer had,
for some reason, decided was worth carrying around. Whatever. Anyhow, a note
about how the archer skills 'find' ammo: first, they check your inventory,
then your quiver, for the specific ammo you name. If you don't name a specific
ammo, it uses the first one of the correct name, which for bow skills is
"arrow". Keeping an item named 'arrow' in your inventory, _and_ not naming a
specific arrow when you fire your bow, is a double-team that will keep you
plucking an empty bowstring and cursing while ogres eat your face off.

How to avoid:
-- don't carry such items in your inventory. Use a bag or a mule.
-- don't carry such items at all
-- keep a bundle of 'real' arrows in your inventory
-- name the ammunition when you fire it.

Shinarae Lluminus

Woocca writeth:
Is it really that hard to make it find the first item in inventory that is
called "arrow" AND is a weapon? Also the item "an arrow" could be removed from
the random items list since there are functional arrows in the game now.

--
Woocca

The answer is yes, because some archery attacks (mostly slings) can fire
things that are not weapons.

Shinarae Lluminus