That scrap of paper fluttering across the road a couple of miles back was your brevet card.
That reminds me of the Staffs Peak 100 a couple of years ago, when my Brevet Card (unknown to me at the time) fell out of my back pocket on a descent. When I couldn't find the card at the next control, I realised what had happened, and where. I continued the ride, picking up receipts at the controls, as I knew the route would later take me back up the hill where my brevet card had fallen out.
The good news was that I found the card without too much trouble
The bad news was that the grass verge had been mown in the meantime, and I only found half of the brevet card.
More good news, though, as the organiser accepted my completed brevet card (what there was of it)