That is disconcerting. Do you mean the pin itself snapped into 2 different segments? Were the collars still ok, or did one of those happen to get bent? May I ask if you happen to have a photo of it?
My old 2220.80 is also on a pin & collar system. Before sending it in for service this year (1st service after 9 years of ownership), I had noticed one pin was starting to stick out a little from 1 direction. Had no idea how it happened, other than thinking maybe one of the collars was wearing out over time... thus losing its hold on the pin and allowing that pin to slide outward over time.
What a stroke of luck (or divine intervention
馃憤) that it fell into your lap. I hope to have such good fortunes myself if I ever experience a pin or spring bar failure!