Picture caption: the album "Three Cheers For Sweet Revenge"
Current Status: Partially Found
In 2003, while recording the Manhattan Demos for the album "Three Cheers for Sweet Revenge", My Chemical Romance recorded a track called "Sister To Sleep". It was never officially released to the public, but was performed at a live show sometime in that same year. As a result of this, a live bootleg has unofficially circulated onto the internet, and is available to listen to on YouTube. However, the studio version remains lost, even to the band members themselves.
Sometime in 2013, the ex-drummer from My Chemical Romance, Matt Pelissier, leaked three random 15-second parts of the song on Twitter before quickly taking it down and claimed that it was on an EP that contained some other Revenge demos and that there were a total of six copies of the EP in existence. However, he could not upload the full song due to legal reasons, on December 30th, 2018, an Instagram user called Solongandfortnite posted the 3 parts that Pelissier had leaked all those years ago. Here is a link to a YouTube video with it: https://youtu.be/F9ze74z1N18