Push it through a drywall wall between studs and it should fall to the blocking at 4' increments off the ground code requires. If you can, put a nail into the hole and hang a painting or w/e to hide the small hole, or some Spackle. Later, use a magnet to attract it through the drywall and draw it back up to a hole or other opening in the wall. Even if the detective saw the hole, the paperclip isn't there, that's just the retrieval and drop point. It'd basically be impossible to find without ripping all the walls out. I doubt they could detect it, even using a metal detector because of all the background ferrous metal in nails, nail stops, Simpson clips, wiring, etc. that the detector would pick up everywhere else.