Found this on the official Muse forums:
A few of us hung back after the gig and managed to find Matt and Dom. Old Man Pigeon asked Matt what had happened to Eternally Missed, and he said it would be the B-side to the next single and that they haven't scrapped it at all!
So there you have it. Unless Matt's got confused again, we'll hear Eternally Missed around 10th November.