Sorry, but we can say with certainty that your character wasn't created in 1.0, hence why it doesn't have the legacy mark.

Enkidoh bought up a good point about the legacy achievements and although your achievements are set to private on the Lodestone, when a character is created it is assigned a numerical "ID" and that number for new characters only ever increments.

Looking at the Lodestone, your character is ID 4854543 and if I go backwards until I find someone with public achievements (just change the URL at the top of the page) I find 4854535. That person doesn't have legacy achievements and their first achievement was completed on 24 September 2013 which was 2.0 (ARR) not 1.0. It's possible they didn't complete that first achievement on their first day (complete 10 quests), but 2.0 had been out nearly a month by this point. Of course you could go even further back to find another public person, but the lack of legacy achievements is really all the proof we need.

As others have said maybe the character in question is on another service account or maybe you did delete it and recreated it when you came back for 2.0 (you didn't sound 100% sure), but the ID number confirms it is not a 1.0 character.

I'm actually curious now as to the ID of the last 1.0 character (it'd be useful to know that for future reference!), but either way that doesn't help you sorry.

Edit: And apparently I took so long working that out/writing it down, you already worked this out... oh well!