Cleonims

same thing happened to me wth

Same here! I am beyond frustrated!

There was a problem a few weeks back; some will come back and others won't. Search in your Reading list some titles may be hidden there.

Yep. Happened about a month ago. Everyone lost all their lists. But lately they've been retuning. Mine have somewhat returned but my now reading have all been put into already read. Around 800 of my want to reads are still missing. It'll likely come back for you too, just a matter of time

only rating and tagged items are coming back. if you get a non-rated or non-tagged back, consider yourself lucky. from updated info by Suujin, it's by date of manga added. not by your account. if by the time the all clear is given, and your list isn't back, you're to contact the email given at that time. until then the suggestion is leave your lists alone. that way it doesn't interfere with the work the devs are doing or if there's another glitch, and you've put a bunch of work into doing things yourself all that work goes poof. you'll just be upset and frustrated. use google or firefox (browser) bookmarking system to bookmark things for now. or some have even used spread sheets to keep track.