(It had not been dropped that I am aware of)
Hey Bubba,
Sorry to hear that. Where does the frypan live when it's being transported? My money is on it copping a hit from somewhere. Cast iron is strong, but brittle. They need to be packed somewhere tight where it can't vibrate/get hit by another saucepan/shake around/etc.
Otherwise all I can think of is what Robbo's already mentioned, thermal shock.
Have you been competing in the recent Australian Safari? Getting a bit of air-time in the camper??
Thanks,
Matto