if you're having trouble finding an arrow in the grass because it went in flat, take your shoes off and walk normally in the area you think it is. You will easily feel the tell tale tubular lump of your arrow.
works even better than metal detectors. (not so good for you if the grass is wet though)
on the same theme, if you missed the boss either left or right but at the correct height pace out 12 steps behind the boss, there's a good chance you'll find it straight away.