Originally Posted by
Mtracer
Well, when I first had odd behavior in 11th and 12th gears, it was about 5 miles into a ~70-mile ride. I'm sure the skipping was caused by a fully broken inner plate. Point being, I put 60+ miles on the chain with that broken plate. .....
About the only thing that's certain is that the interval between a single plate failing and the chain snapping is very short.
The chain simply cannot handle loads with a broken plate. So, while it's barely possible you rode a while if you were gentle and there were no hills, I suspect the link broke much closer to when you saw it.
Possibly it was ready, and you finished it off with side load when trying to open the connector.