Presenting the stone, then, not finding it. In which case the vision would likely not be portraying the stone's original location and/or the means by which Bellatrix had obtained it.
That's assuming that the stone is hidden somewhere and the mirror merely allows information on its location. In canon, (or, at least, going by my memory of the movie) after HP saw himself in the mirror finding the stone, it materialized in his pocket.
New chapter!
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 104.
There is a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: