I think it might also refer to something in-game, as well, that maybe we haven't discovered much of yet and won't until ARR--something like a guiding light/guardian for adventurers, or any travelers for that matter, aside from their patron deities. In Merlwyb's speech for the Maelstrom during the first GC quests where you take time to pick your Company, she says something like this to finish hers off:

Quote Originally Posted by Merlwyb
The Maelstrom has launched, its final destination a new Eorzea where Limsa Lominsa's founding principles shall shine like the lodestone and reverberate like thunder, till sea swallows all!
Instead of calling it just 'a' lodestone, she calls it 'the' lodestone--which means either:

a) There's only one real lodestone and it means something more important in Eorzea than we think of it.
b) i'm overthinking it--she's just making it sound fancy and there's actually lots of lodestones in Eorzea. (this one is very possible.)

also on the subject, I think someone, somewhere, in some quest mentioned something like "the lodestar" in 1.0. I know that's not specific at all but I distinctly remember the NPC saying it. It's possible the lodestone/lodestar are different names for the same guiding light that keeps adventurers on their way, or they're two completely different entities that were barely touched on...ugh, but now I wish I could remember which quest/NPC it was that said that! if i find it i'll get back to you on that.