Physically go replace it or try to replace it/buy somethingelse and it will reappear magically.
I lost my Passport. It was gone for months. I went to the PO, picked up the paperwork to start the process over. Stuck it between the seats in the car for the trip home and it slid down like half under the seat. When I reached to pull the paperwork out, my passport was there too. I swear I looked there four or five times.