What this has me thinking about is all the supply chain disruptions of the past few years. We're sort of living out a much lower stakes version of your thought experiment. I haven't seen a compelling treatment of how a market could maintain optimal redundancy in the overall system of trade.

Still, the gains from specialization are so great that I don't think colonies would generally operate in autarky. What makes more sense is that critical resources would be stored in enough quantity that if something disrupted the supply there would be plenty of time to ramp up domestic production.

That would probably have to be a non-market policy, though, since markets don't seem to operate that way on Earth. Although, perhaps it would be an insurance requirement.