Greetings and welcome!

I'd suggest contacting support via the support site:

https://support.eu.square-enix.com/index.php

(May want to click for your region on the top right there.)

These forums here can't really help with account related matters, so that's the only option here really.

I have a feeling they can't help either though, as in, gotta buy it again... but I'm hopeful they can!

I suppose if bought via Steam, there is that refund policy, though I think the registration code(s) would still be lost since they were already used up.

In any case, best of luck with sorting this out!