So when I launched osu! just now, I got an error message talking about how my beatmap folder had gone corrupt or something, and it needed to be reset or something like that.
So I clicked the error message away, launched osu and went into solo and it took a while to launch the beatmap screen, I assumed this was because of the apparently corrupt beatmap folder osu! told me I had.
Fast forward a few seconds and I'm scrolling through my beatmaps, and literally all of my local replays have been deleted, there's no local replay left on any map.
I tried asking for help on the #help chat and I got told that there was no way for me to retrieve my local scores, even the few scores that I had saved in the replay folder couldn't be imported, because when I tried to do so, osu! told me that the beatmap for the replay was missing, even though I did have the beatmap, this happened with every replay I had saved.
And after talking with someone from #help, I found out that this isn't an uncommon problem, and it has happened many times before that someone lost all of their local scores.

Now the reason that I'm writing this post isn't to ask if there's any way to retrieve my local scores, if there's a way to do so, I'd love to hear that though.
The reason that I'm writing this post is with the slightest hope that Peppy or someone else high up in community will read this.
I'm just devastated that the way local scores are saved is done so badly, I really wish that there was just a map with all the local scores you've set, that's just there as a backup, just in case something like this happens to someone, and I don't care if it's just the scores and not the replays, I also don't care if that's going to take up space on my pc, and I don't think anyone who's encountered this problem as well cares about those things.
I just really wish that this problem would be fixed so no one in the future has to run into this problem and lose all of their replays without any chance of getting them back.

I just lost about 3-4 years worth of local scores and consistently seeing that left side of my screen empty just made me lose all motivation to play.
I won't stop playing osu!, but I've definitely lost my will to play for the upcoming time.
Not being able to see how much progress I've made, not being able to see how many times I've choked at a certain point in the map, not being able to see any replays I really liked, but that weren't good enough to be my global top score, all of these things just crushed my whole experience of playing osu!.

Please Peppy, I don't know a lot about coding, but I'm sure it shouldn't be that hard to just make a folder that saves and backs up all of your local scores.

EDIT: I just noticed that also about half of my maps are gone, I lost about 5.5K maps, does anyone even know what happened?

Inside your osu! folder is a hidden folder called "Data" and inside that is another folder named "r". This is where all of your local replay data should be stored (this is different than the replays folder). Check to make sure that there are actually a bunch of .osr files in that folder. It's likely that there are still a lot in there (you can actually backup this folder if you really want to). If none of the things I'm about to suggest work, it is possible to manually reload all of the .osr files back into your game so you can see them again.

Press F5 on the song selection screen and let your beatmaps reprocess again to see if the 5.5k maps you are missing show up again. Even if your database somehow became corrupt and had to recreate itself, your beatmaps and replays should not delete themselves. They are still in your osu! folder, they are just not displaying. If they do appear, restart your game to see if your local replays appears as well.

If that does not get the other beatmaps to reappear, there are a few things you might be able to do. Open your osu! folder and then close your game. If there is a file inside your osu! folder called "osu!.db.##############.bak", rename it to "osu!.db" replacing your current "osu!.db" file. Make sure you have file extensions enabled through Windows so you aren't just renaming the file and you actually change the extension. Restart your game, your beatmaps might reprocess, just wait for them to do that and then check to see if your other songs are appearing.

If you do not have an "osu!.db.#############.bak", move your current "osu!.db" file outside of your osu! folder, start the game again, and then let your maps reprocess.

If your local replays are still not appearing after following and of the above steps (assuming the files still exist in "Data\r"), close your game again, remove the file "scores.db" from your osu! folder, and then restart. This database file should be recreated from the scores in that previously mentioned folder.

Death wrote:

Inside your osu! folder is a hidden folder called "Data" and inside that is another folder named "r". This is where all of your local replay data should be stored (this is different than the replays folder). Check to make sure that there are actually a bunch of .osr files in that folder. It's likely that there are still a lot in there (you can actually backup this folder if you really want to). If none of the things I'm about to suggest work, it is possible to manually reload all of the .osr files back into your game so you can see them again.

Press F5 on the song selection screen and let your beatmaps reprocess again to see if the 5.5k maps you are missing show up again. Even if your database somehow became corrupt and had to recreate itself, your beatmaps and replays should not delete themselves. They are still in your osu! folder, they are just not displaying. If they do appear, restart your game to see if your local replays appears as well.

If that does not get the other beatmaps to reappear, there are a few things you might be able to do. Open your osu! folder and then close your game. If there is a file inside your osu! folder called "osu!.db.##############.bak", rename it to "osu!.db" replacing your current "osu!.db" file. Make sure you have file extensions enabled through Windows so you aren't just renaming the file and you actually change the extension. Restart your game, your beatmaps might reprocess, just wait for them to do that and then check to see if your other songs are appearing.

If you do not have an "osu!.db.#############.bak", move your current "osu!.db" file outside of your osu! folder, start the game again, and then let your maps reprocess.

If your local replays are still not appearing after following and of the above steps (assuming the files still exist in "Data\r"), close your game again, remove the file "scores.db" from your osu! folder, and then restart. This database file should be recreated from the scores in that previously mentioned folder.

I don't know how to find that hidden folder "data", but I'll try the other stuff you've suggested and I'll get back to you after that

EDIT: I've reprocessed my maps and the missing maps have reappeared, however no local scores have turned back up and there's still a small issue with the previously missing map, they don't automatically show me what rank I have globally, with every map I have to go to global rankings before my rank appears next to the map.

I've also tried opening the few saved replays I had in osu! again and that seems to work now, so I have at least a few replays back.

Data is a hidden folder which means you'll need to enable hidden folders through Windows to see it.