Board Thread:Questions and Answers/@comment-108.219.33.152-20151212080309/@comment-6697950-20151212134752

You can't find it because it hasn't been released. The track was first used in the Extra Edition, but it still hasn't been published in any OST. An SAO Music Collection, which will include never before released tracks, will come out in January, so you should come back then. It might finally include the mysterious track that everyone's dying to get.