He was restored from a V2 Horcrux that was too well-hidden: without the Resurrection Stone network (Horcrux V2.5?) he was dependent on someone touching his horcrux, which didn't happen for a long time.
Well, as he said, it was an "obviously hidden" horcrux screaming "I'm apowerful magical artifact" (like the locket in book 6, which he explicitly calls out), as opposed to a random pebble in the middle of the desert.
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 120.
Plans for next chapter release:
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.)