We're looking into a few cases where mobile live streams appear deleted if metadata (title, description, tags) or change privacy setting (public, unlisted) is edited while processing. It shows: "the video has been removed by the user". Thanks for the reports–updates to follow!
@teamyoutube I will pass this along to those that I know have experienced a problem, however, I do know that for a few of them, changes while processing were not part of the equation.