This is a little different, but for awhile I drove a few beater c900s and I would always set stuff down on the rear spoiler and forget. Every time though, believe it or not, the stuff on them would not fly off! This happened with sandals, shoes, even a few wrenches one time.
One time, one of my brother's friend's left a big hunting knife on the spoiler as him and my brother were hanging out in my garage by the back of the car. Early the next morning, I'm driving to work, speeding a little, and a cop comes out of nowhere and pulls me over. I'm almost late for work so I just want the cop to cut to the chase so I give him my license, registration, etc. He goes to his car, runs them, and then gets out and starts to walk to my car. As he nears the rear bumper he stops and goes to the rear center of my car. I'm like "what's this guy doing?" Moments later, he walks to my window with the gigantic hunting knife, saying "what's this?"
Suprised because I had no idea it was there, I say "That's not mine." He replies "It's not yours?" I'm like "no, i don't know who's it is..." as he looks into my car. I continue "...you can have it if you want." He says "I don't want it." I say "Neither do I." So what the cop does is take the knife and throw it deep into the woods lining the road.
Funny story, b/c I WISH that had flown off of my car. Even crazier thing was that I didn't get a ticket!