Accounts are disabled while they are being renamed, as stated on the help page:
While the rename process is running, you cannot edit on Wikia (and thus will see a message informing you that are blocked)
What he means is, can he get his old username back?
No. That account still exists, it's just disabled, for whatever reason. You can't merge accounts. If you want to know why your old account was disabled, use Special:Contact/general. It was disabled by user choice, or by Wikia - not some idiot. Unless you call yourself some idiot.
Thanks. And yes it was user choice, the guy did it on my account the time I was gone.