Try 'fish tape' from the hardware store, Lowe's/HomeDepot, or a straightened out coat hanger...and maybe add a bit of tack tape on end.
And, if that truck is metal/slightly magnetic, a magnetized 'poker' tool, often available at an auto parts store is worth a try too. I drop/lose nuts, bolts, whatever regularly when working on my m'cycles and that mag poker saves my butt.
Worth a poke.
GL, mD