Other users seem to be experiencing similar issues I recommend reporting this incident to the Google Issue Tracker. This could help accelerate a resolution and you might also find updates on any fixes or workarounds from the community.
Same thing here. I was working on two Looker Studios reports that go out monthly, and today they’ve completely disappeared without a trace. Has anyone had any success retrieving their reports, or are we all up a creek and rebuilding everything?
UPDATE: Just as mysteriously as my reports disappeared yesterday without a trace, they have magically reappeared this morning. I have now saved backup copies of everything!!