This is what happens........

I drill the pin hole a bit wider then put a long shackle keyed lock on it. This way they can not just pinch the tongue .

I agree gbc, they probably thought they were being "funny" & imagined the car driving off & leaving the trailer behind!

Padlock is probably a better solution than those wonderful self amalgamating lockable pins that you can never get undone again. I swear half the towball snatch recoveries in the last 20 years would have been done because they couldn't get the tow hitch out.

gbc. I think you are spot on with the lockable pins :-)

Had that happen to me towing my work trailer.
Come off at about 60kms hr, safety chains held it to the vehicle.
Now use a 5/8 bolt and nyloc nut, needs two spanners to undo now.
Charlie

Twice now my neighbour has gone off with no pin in his hitch. Lucky for himor somebody else the first time I was out working on my car the second time his wife went off 5 min after him. Both times we gave him a call and he took it off and returned.