This isn't intended to sound like an "I told you so" but I've seen this dozens of times. Nobody ever gets their account back once it's gone. I'll tell you what I think happens. Gree accidentally loses/deletes your account during the transfer process and they lack the balls to tell you so they just completely ignore you and pretend you don't exist until you go away.

I'm supposed to be getting a new iPad (keeps getting delayed) but I kind of secretly hope Gree loses my account when I try to transfer, too. That way, I have no excuse to finally quit this garbage for good.