This is most unfortunate. I looked through Astro's history, unfortunately he did not post an bitcoin address anywhere, so it will be very difficult to prove who owns the account now that it is locked.
arkab can strengthen his identity by posting an image of this coin (which is unique in terms of ANACS serial and vanity prefix) next to a paper slip with his new username.
It would properly not be enough to have theymos restore the account, but at least it would provide you prof for future transactions.
Under these circumstances is escrow mandatory - TheAnalogKid is already on top things in regards to this.
Good luck to both of you.
I have a bitcoin address posted in my PMs back from 2011 and have signed a message to Theymos with it, so hopefully that will sufficiently prove my identity.
I will post an image to this thread just to give TheAnalogKid a little more peace of mind and to strengthen my case with Theymos.