Mine has a piece that bolts onto the bike, and a pin in case that slips, and a strap in case both of those fail. The other end that attaches to the trailer is much like a hitch pin but with a keeper to hold it in place.
The woman's trailer must not have been attached correctly and the safety devices not used or maybe it was just a super cheapo with no attention to safety? I couldn't imagine a trailer manufacturer not having a back-up safety device.