That's not necessarily how the US civil court system works. Courts will sometimes throw out or alter contracts if a good-faith mistake by one party produces a result that would violate the fundamental principle of equity. This is more likely if the result appears to violate the original intent of the contract.

That's very true; I should have looked this up before stating it. Edited my original comment

> And even if it were, why roll back the block chain to rectify the situation? In traditional accounting, wouldn't you need a ledger record of both the mistake and its correction?

This is exactly what happened. The blockchain wasn't rolled back. New transactions crediting the victims were injected into it.