Sounds like either the ball was the wrong size, the hitch was not latched properly, or the hitch had excessive wear. The trailer's balance may have been off & may had little to no weight on the tongue. There is a reason that it came unhitched. More issues than just overall weight.
I am positive there is alot more to this story.
I have seen some scary home made trailer as well.
I have seen a trailer driving a car down the road due to improper loading. How the guy kept control of if he did I will never know.
I have also seen many trailers on their side but the tow vehicle stays attached.
