I think you're underestimating how guessable things can be if one pays attention to clues. I can't remember for sure, but I think the possibility was in my mind since I first read the note about how Harry should have noticed his confusion about the story.
The list of evidence I gave in favour of that position in a Hatrack forum discussion back in November 2010 was simply that
a) We're told that Harry should have noticed something off about the story, but he didn't (simplest thing he should have noticed is: how the hell do people know what Voldemort tried to do, if there were no living witnesses)
b) Avada Kedavra normally leaves no mark on the victim. Whatever was done on Harry left a lightning-shaped scar.
c) Avada Kedavra kills anything with a brain and never rebounds. This time it's supposed to have failed to kill Harry and to have rebounded onto Voldemort.
All of these were well known before chapter 43.
Since then we can add the evidence of:
d) Bellatrix indicated she was given Voldemort's wand before Voldemort went to the Potters' home -- simplest explanation was that Voldemort didn't want his wand taken away by Aurors when his physical form was destroyed, and so he knew his physical form would be destroyed.
e) Lucius Malfoy seemed to believe Voldemort resides inside Harry's body, which is a rather odd conclusion to arrive at, unless he already has reason to suspect Voldemort wasn't attempting to kill Harry.
These pieces of evidence are not in chapter 43 either.
What evidence are you talking about that's in chapter 43?
a) We're told that Harry should have noticed something off about the story, but he didn't (simplest thing he should have noticed is: how the hell do people know what Voldemort tried to do, if there were no living witnesses)
b) Avada Kedavra normally leaves no mark on the victim. Whatever was done on Harry left a lightning-shaped scar.
c) Avada Kedavra kills anything with a brain and never rebounds. This time it's supposed to have failed to kill Harry and to have rebounded onto Voldemort.
Were you aware, at the time you made the prediction, that
(And somewhere in the back of his mind was a small, small note of confusion, a sense of something wrong about that story; and it should have been a part of Harry's art to notice that tiny note, but he was distracted. For it is a sad rule that whenever you are most in need of your art as a rationalist, that is when you are most likely to forget it.)
Why does the wizarding world believe Voldemort used the Killing Curse on Harry? Whether or not the Love Shield exists in MoR, I doubt most wizards had an >epsilon prior for the Killing Curse resulting in a scarred but otherwise unharmed target, a dead and burned spellcaster, and a destroyed building. There were no surviving witnesses except Baby Harry. Where did that version of events come from?
If I was Joe Random Wizard and heard that evidence without names attached, I would naively hypothesize: Dark Wizard shows up at house, encounters mother + father + their allies. Battle ensues. Parents and Dark Wizard are slain. House is destroyed and baby is hit by debris. There is one obvious question - why the allies didn't take the baby with them - but any answer to that is more plausible than "There were no allies; the most reliable curse in the world backfired on its most experienced practitioner."
Not that the "reflected curse" story was hard to sell. People are great at not asking the next question when they want to believe.
We have some additional information about the events of that evening:
What really happened at Godric's Hollow?
PS. If the Love Shield does exist in MoR, do you suppose Bellatrix could cast it?