We all know that the dragons apparently disappeared in the year X777. At the same time, Lucy's mother, Layla Heartfilia, died at the age of 29. I don't know the cause of her death, it's just that I know she passed away at the same year.
Layla Heartfilia seemed to be a powerful Celestial mage given that she had three Golden keys (Aquarius, Capricorn, and Cancer; these three are pretty powerful too) and she probably had more than that (Silver keys or something).
It hasn't been mentioned whether Layla died the same day the dragons disappeared, just that it's the same year, or has it? So I was wondering, could she have had some sort of connection with the disappearance of the dragons?
Yes, the truth about the disappearance of the dragons has been revealed and all, but I still think that there's still something behind this.
Too bad the dragons can't reveal anything anymore.