He is sure that is the account that he was using in Settings > iCloud on the phone - if he logs into the account on http://www.icloud.com does it show in the Find My iPhone section of the account ? Only the account that was being used in iCloud on the phone can reactivate it.
If he's sure that it was that account then he could try going to an Apple store, or contacting iTunes Support online, and see if they can remove the phone from the account - they are likely to want to see proof of ownership before they might help e.g. original receipt with the phone's serial number on it