It happened in January. Mangago's data disk crashed. Everyone's lists got fucked. Only rated and/or tagged stories were recovered, nothing else will come back. All stories were dumped into your "Already read" list.
Take this as a lesson everyone, nothing online is here forever. Keep offline backups wherever you can, and don't rely on a single website for stuff like this. I learnt this long ago so I kept an offline list of my to-reads updated as I went, but I won't be trusting them with anything other than viewing a story now.
I'm sorry for everyone who is experiencing this type of loss for the first time. Please, take it to heart and think ahead next time.
Did mangago reset the I want to read, I'm reading, already read list? I'm literally crying because that's my only way to organized things and find manga that I forgot.