Glad you were not injured and THANKS for the heads up as I also carry chains and a crowbar on my platform at times. If tractors had a decent sized toolbox it would encourage us to keep the stuff out from underfoot.
Reminded me of something that happened back around 1979, I was driving a rented Ryder cube van and the glass soda bottle the prior driver had stuffed under the seat rolled out under the brake pedal as I made a fast stop. Well, TRIED to make a fast stop. BANG. Good thing it wasn't a beer bottle as I had difficulty convincing both the police and the rental agency it wasn't MY bottle. Always checked underseat on a rental truck after that !!