Is this a US, Japanese, or European save?
Someone in another thread gave two Japanese save files (one before entering the gamesync id, and one after). I was able to find where the game sync ID was located in that version and the US version, but I have no idea how it's encoded (nor have I looked at it since). If you have the Japanese version, just for kicks I could try to
(technical stuff)
reset it so you never entered the game sync ID. If you don't have the Japanese version, we could still try, but I'll need any save before entering the game sync ID and the same save immediately after entering the game sync ID (not that I'm asking you to make these, it takes a lot of time and there's no guarantee that it would work).