Edit: I can't find anything in the Blockstream whitepaper to support tvbcof's claim that one can recover their assets from an attacked chain. The closest is section 4.2 Fraudulent transfers, but the only really viable action there is to dilute everyone's BTC by the amount of the stolen coins.
Who is going to do that, some administrator? No.
The best that could be achieved would be to build in some sort of rules like that into the scripts. No concrete method for doing that is proposed, but even if it were, it couldn't possibly handle all possible failures, since some if not all failures are by definition unanticipated. In the event that the state of a side chain were scrambled, there would just be no way to know who should be able to redeem.
For this reason, even the hint (or in some cases merely a rumor) of a problem on a side chain will lead to a run-on-the-bank scenario.
the way it would need to happen in normal circumstances is for the scBTC to be mined back to BTC, by reversing the proof, most likely via merge mining. since the most common cause of a failure is likely to come from a 51% of the SC since it is inherently less secure (<100% MM'd) by definition being able to get mined back is not going to happen. after all, that would be the purpose for the attack; to kill off everyone's scBTC while simultaneously shorting scBTC on an exchange while going long BTC on the MC.
that would be a fun attack.