If the buyer had reformatted the HD immediately after buying it, would that have made it impossible for the seller to lock it? Could the buyer have changed the

If the buyer had reformatted the HD immediately after buying it, would that have made it impossible for the seller to lock it? Could the buyer have changed the account which it was linked to without going through the seller? Of course a bill of sale would also have been enough to get Apple to help, according to another comment. But even that is not hard forge.