So, after some digging around this actually seems to happen every once in a while:
Status is “Investigating”, which is the Gems of War way of moving unsolicited mail that won’t be looked at to the spam folder.
Do what the other reporters did, open a support ticket asking that the mythic gets issued to all the guild members who missed out due to the bug. Apparently you’ll have to send a reminder or two before anything happens, so be sure to check with your guild mates that they all were properly compensated.