Unfortunately I have never signed messages in the past for bitcoin addresses.
That's okay, if you have access to one of these addresses below (with a note the addresses were posted before the hack), now you can create a signed message like the format above and post it in this thread.
15RpAVXVJorcVbokqDD5s1xN4iDYeibyEZ
18uLw9HQNYmJ218YMQKNGE7mHDu3ftc11e