Got my own horror story.
Taking an old sectional couch to the Salvation Army.
Loaded it in, one piece nested upside down on the other, and strapped it down.
Went inside to get my wallet, came back out, hustled all the kids out of the various "spaces" between the cushions and into the truck and off we went.
Got onto the main road, just got up to speed, and came out into the open. Looked in the rear mirror to see one section "bounce" upwards. Hit the brakes. Too late. Next gust lifted it out of the truck, flipped it over, and it landed rightside up on the road beside me. I'm already on the brakes, so the dang thing passed me, doing 60kmh downhill. Had great little hardwood feet with steel inserts, so it just kept going, me chasing it. Lady coming the other way saw the whole thing happening, came to a stop, but couldn't get out of the way. Broke the front light, but that was all. She was real good about it . Turns out she sold furniture for Sears, and the only reason I was getting rid of our old one was that we had a new one delivered that morning - from Sears. She was killing herself laughing when she phoned her husband and said "Honey - Guess what, I was just hit by a love seat"
Moral of the story. Just cause you tied it down when you loaded it, doesn't mean it's still tied down when you depart. My strap was in the way of the fort playing so the kids removed it. Now I always check everything right before I drive off. Since saved me losing my hitch mount bike rack once, when the hitch pin was sitting on the bumper.