Veryl lucky, I also tie everything down, but have also recently after stopping for a drink, fuel etc now go over everything prior to departing as I had some smart a$$ undo the tailgate, my bad for not locking it but it had been off for repairs, it is amazing how much that tailgate swinging around made everything jerk and unstable. Luckily like you nothing happened except for some swearing and madly trying to get off the gateway