I think anybody that hauls regularly has done something like that.
I have two:
First, a brand new trailer behind a brand new pickup. Happened to be driving home from work and noticed a guy baling hay. I'd been having trouble finding a source for hay, so I stopped and asked if he was selling any. He was, so I hauled booty home, hooked up my trailer and hauled booty back to the field after picking up my grandson to help.
All good until I went to hop up on the back of the trailer (an 18 foot double axle "landscaping" trailer) and between my weight and the weight of the bale, the hitch came off the ball. I'd never fastened the latch and the only thing keeping the trailer on the ball was tongue weight. Scared the whey out of me thinking about that trailer coming off as I was hauling butt down the highway.
Second one, older truck older trailer. Had a landscaping job where the use of a small dozer would GREATLY speed things up. Acquaintance had an old John Deere 40C crawler and he said "Sure, just put some gas in it when you're done". Hooked up the truck and trailer and went and got the dozer. Got it up on the trailer (a bit more exciting than I was used to right there...) and inched it forward watching the back of the truck to judge balance and tongue weight.
Got it where I wanted it, shut it down, put it in gear and set the track brakes. Stowed my ramps and started looking at tie points to chain it down. And then I had a HUGE dumba** attack. I decided that with that much weight, steel tracks, brakes set and in gear, it wasn't going anywhere and I didn't need to chain it.
Rapidly turned into a good news/bad news situation. When I stopped (quite gently) at the end of the guy's driveway I looked in the mirror and watched that dozer slide along the treated lumber deck of the trailer, watched the blade drop off the front of the trailer and clean the tongue jack right off the trailer, stopping just before bashing into the tailgate of my truck.
Good news is, it happened before I got out on the road, and as far as I know, nobody saw it.
Bad news is, I wound up needing a new jack, a new hitch on the trailer and a clean pair of shorts...