By your profile pic I presume you're a hunter.I put reflective tape on everything big enough for it to stick to but small enough to carry around.
Some folks make a hobby of that, magnet bridge fishing. Had my minnow trap caught once.Fishing off a bridge I leaned over the gaurd rail and heard my knife bouncing off it on its way to the river.
Big magnet, some rope, and a couple of casts, got my knife back