Senior Camrose, fortunately with screens. 2H was not alerted on East's side, but was correctly alerted as weak on West's side. North asked East when West raised if 2H was weak. At this point, East, Muggins, realised that West had opened 1C, not 1S as he had thought. I don't think there is any real problem with screens, as the actual auction is authorised, and I chose 6H which was a small gain as one pair missed it.
Without screens it would be interesting, as the alert of 2H would wake East up to the fact that he had misread the auction. Is East allowed to realise his error, or must the "unexpected alert" mean that he must continue to think his partner has opened 1S? Something like QJxxx Jxxx KQ Kx would offer no play for slam and the five level is not safe.