Aonuma said that Link was a normal boy (I assume this means not a thief), and --I was going to say that he received the sword, but I just rewatched the interview and he only said he "got" the sword. Of course, that's the English translation so it may have been more specific than that in Japanese. Anyway, I was going to say you're wrong, but now I can't. He said an event occurred that revealed the land below and forced him to go there, and that event was "get"ting the sword. I assumed that someone gave it to him, but thievery isn't completely ruled out. But I wouldn't give it an ounce of thought since Link's not like that.Maybe the Ooccoo will have both the dominoin rod and the Skyward sword stolen by link.
I don't feel like looking for it, but something in mid-2009 mentioned that it had been in development for four years and that it was almost done.Were does it prove that ZSS started midway into TP? All we know is that TP started in 2004, and ZSS was mentioned since 2009.