Yep, definitely a lucky goober. And good for you, I'm glad you didn't lose anything. Happened to me twice. Once my lists were gone and came back. The other time nothing happened when the whole site was freaking out, and the 3rd time now they are gone again. Overall, it's the system just being picky and eventually everyone will get there stuff back it will just take time.
No it just came back, I did personally rebuild it brick by brick in another place before I knew it would return cause I thought it was lost forver and I was too afraid to ask in the comments for help so I managed alone. Was a waste of time since everything came back but good lesson to always have a backup save method. But no, you won't have to rebuild brick by brick, there MIGHT (very little might) be some mangas missing, but that's just a what if scenario cause you know +1300 is a lot and some might not show up but I doubt it since this never happened to me just something I wanted to put out there as a possibility. So no you won't have to rebuild, but I do suggets you start making a backup method in case this happens again.
I use a Word document with a table. The columns are titled story name, link, and a short synopsis. Whenever I find a new manga, webtoon, or anything I like, I just add it to the list.
Later I moved everything to an Excel sheet, but I stopped updating it and went back to the document because it is way easier to edit. It takes a bit of work to set up at first, but once it is done, it is super easy to manage and you have it forever. You are not relying on a site to keep track of your stuff.
You could also use Google Docs. I made mine before Google Docs was really a thing and was too lazy to switch.
If you want to stay on the site, you can create manual reading lists. Those usually do not disappear. Bookmarked chapters stay too. You can also tag manga you save, and those tags still link you back to your reads.
There are also sites like Anime-Planet or MyAnimeList, but honestly I like the document method the most. It feels the safest and least likely to get lost.
Hope this helps.
Last time it was a few days (4) for me to get everything back fully, but I'd say in general give it till next Monday at the very latest but it all should be back way before then. Only reason I say Monday is cause people are still spamming the site with comments which can overwhelm or slow down a recovering system, making the process a bit longer.

Uhm so y’all are tweaking that y’all’s lists are gone or smth, but when mangago game back online for me, my list was still there… Am I lucky goober or smth ‘-‘ It got rid of some of the manhwas on my list and a random one was added tho…. So….