I laid a hitch tending pulley, friction cord and carabiner on the back of the wifes car in garage one day and forgot about. I wonder if the person who found it even knew what it was for.
I don't care if people put stuff on the hood of the truck. If the driver can't see it on the hood, they can't drive my trucks.
It's not the lost gear that is a big concern to me, its causing an accident from losing part of my load.
Last time I put something on the roof of the truck was a handful of years ago. The coffee cup slid right off the roof, going about 35 on a sometimes-busy two lane road, into the oncoming lane where people are often doing 50+, which was thankfully empty. The cup surprised me making a funny sound on the roof then coming into my field of view. It exploded when it hit the ground. An erratic reaction can lead to loss of control quickly.
While I've lived in Olympia, someone lost a 2x4 off their trailer on the highway. A woman's face found it.
As much as possible, I clip/ connect things together, and put everything in one staging area, if not next to the truck/ into the truck.
At the first company I worked for, I found the climber's rope when another guy and I finished up the job the next day. Oops.
Another company working at the same jobsite as me left an MS 660 (this is the company that they didn't want rigging over their house). I found it. The crew came back to get it, telling each other, 'Don't tell the boss we left it".
Often, people will put everything in the truck and say, "is that everything?". I mentally inventory my stuff into the truck. Stuff is too expensive to lose. Finding out that you don't have the tool to do the next job, at the next job when its needed, adds to the expense.