@Tempest Blaze: I'm not in Rathio, I'm in those islands where you've to go rescue Lumos, and after the battle with Dark Lugia you dive in order to save Sky, even though you don't have the MO yet, and then once you talk to her you return to the surface, but as you can see in the screenshots, I didn't return where I was supposed to return. Your assumption is probably correct though since I remember I got the message you get once you want to return to the surface even though I didn't have the MO before Sky started talking about returning, so probably something similar like Surfing when you're not supposed to do so when talking with people near the water and so on happened here, but still I can't believe this would result in appearing in a part of the map that it should be impossible to be there in the first place, I wish they actually did a better programming of the game before releasing chapters like this, especially when the bug of Surf should be something they must know already by now.
Anyway thanks, I'll try and see if they answer me in Facebook.