Happens to me every now and then, usually because I forget to secure the tongue on the ball. (needs new coupler: quick fix is a pin that sometimes gets left on the chain where I store it, rather than through hole on top of coupler designed for theft-prevention lock).
My personal sequence goes: hitch/load trailer, drive off. Wonder a few miles later if I remembered the pin, listen intently for grinding/scratching/s****ing sound after each bump. If sound heard, or safety section of brain engages, brake & pull over to rectify.
Helps that I was taught to cross chains underneath trailer tongue to act as weightbearing cradle. Amazing how few Uhaul techs don't do this!
Sometimes I also have to jump on the tongue to get coupler to set. The part that holds neck of ball gets crossways and doesn't want to slip into place.
Luckily it has only jumped w/a light load & trailer is well balanced -- prolly a different story w/firewood etc. And I don't take it on the highway, it's just a utility trailer, for now. Tow chain hasn't snapped but quicksnap gate got bent...
Yes, new coupler is in the works, along w/either new fenders, reflectors, uprights to hold roof top tent and some repair welding, or with a different trailer, depending on opportunity & cash flow.
Hope this helps, another idjit