I don't know if pilots for shows that weren't picked up count as lost media, considering the media isn't so much lost as it is simply locked away. This pilot was created 3 or 4 years ago by Invader Zim creator, Jhonen Vasquez and Rick and Morty production engineer, Jenny Goldberg. The pilot was made for one of the Disney channels, but was not picked up for a full series. You can see a few brief clips online, like this: www.youtube.com/watch?v=-OFCiL7USHY
The premise was: 11-year-old Frolie moves into the Very Important House and suddenly finds herself in the role of caretaker of the universe. And I have to say, everything about this show seemed right up my alley, as someone who loves shows like Invader Zim, Adventure Time, Regular Show, Rick and Morty, Gravity Falls, etc. etc. This show looked like it was right in line to be a hilarious cartoon with a compelling ongoing story while be accessible to both children and adults.
When it wasn't picked up however, it became sealed away by Disney, Jhonen claims that in order to get ownership of the pilot back, he'd have to fork over $500,000 which he claims he simply doesn't have laying around. So not only is there next to no hope of it getting a second chance at life by being pitched to another network (like Adventure Time was when it didn't get picked up by Nickelodeon), but it doesn't seem likely that we'll ever be able to even watch the full pilot. And that sucks. I suppose in theory if enough people funded $500,000 to donate to Vasquez and Goldberg to buy back the pilot, it could then be seen by the public, but I know that's not at all in the cards.