I discovered Calico is still in business. They managed to survive the hi-cap magazine ban. So I gave them a call.
While they have never heard of the exact failure mode I had, they said that with the older bolt design (which my gun has), they have seen a few rare cases of the gun firing out of battery as the bolt is closing. As Armed Canadian pointed out the bolt was damaged when the shell ruptured. For around $100 they’ll repair the bolt and upgrade it to the current design. If I ship them the whole gun they’ll clear the barrel, inspect everything, and test fire it.
The people in charge of the gun club where the accident occurred are interested in what happened, so I’m going to do a little show and tell there (any maybe give them my eyeglass lens to stick up on the bulletin board), and then I’ll probably ship the gun off to Calico.