Don't forget that stainless won't stick to a magnet.
If you don't find it, pull the intake off, that should give you a 90% chance of finding it. The only possibility that you don't find it in the intake or in one of the runners would be that it managed to slip by an open intake valve. Unfortunately, that would mean taking off at least one of the heads.
Good luck on your fishing trip and don't forget that you can find some of the good ones in the most unlikely places.
Wayne