...and now all of my achievements are gone! I tried searching around the internet and came across some kind of 'import achievements' thread from a couple of years ago, but it doesn't seem to be relevant anymore :( If anyone could point me in the right direction I would be eternally grateful!

Hum. I vaguely remember something like that from when I first joined... But I'm not sure. I think you should just send in a ticket about it :o

Yeah there was an extra page that would import your achievements to the new achievements site.

They changed the links though, so your best shot is just to file a ticket.