I'm starting to think a Link to the Past is actually in the Child timeline. I'm thinking that because Ganon's story says he was captured by a combined effort of the Sages and the Knights of Hyrule...not by Link (Who is the person who stopped him in the adult timeline) so than it becomes clear that even though Link WAS able to warn the king of the events, Ganondorf was still somehow able to break the seal and enter the sacred realm.
Also, if you play Wind Waker, you find out that the Triforce of Courage that Link possessed in OoT left him when Zelda transported him back in time and stayed in the Adult timeline (Which was than broken into pieces) so Link of OoT being transported back in time (To the child timeline) Didn't have the triforce of courage, which probably returned to him as soon as Ganondorf broke into the sacred realm.
Edit:
Of course, Link could have been a Knight of Hyrule, in the child timeline.
The ancient hero guy (The shade or whatever he is called) wears nightly armor, apparently walks like OoT Link, and talks about being a chosen hero (Also, shaped his sword like the Master Sword).