I use a locking pin to hold the stinger in the receiver and a small padlock on the coupler latch. Cheap insurance against petty vandalism.
Another forum member had his stinger stolen when he was unhitched and parked attending an event. It was several hours' round trip late at night to buy a new stinger so he could check out and continue his trip the next day.
I let a youth group use my utility trailer at a camp out. At the end of the week, I led the way out 3 miles of dirt road pulling the Scamp
. They followed in a van pulling the gear trailer. We got to the main highway and I looked and said, "Where's the trailer?" As we discussed the situation, another group in a pickup truck came up behind. They were all laughing as the window came down and the driver said, "Lose something?" It was hitched (and properly secured) to their truck.
Moral- trust, and verify...