For some reason the a lot of my albums have been removed from my library. They haven't bee removed from Spotify, just my library. This is a huge pain because it was probably somewhere in the region of 100 albums of which I can't remember a lot of them. This is also the second time this has happened and it took me a few hours to rectify last time and I cannot be bothered to go through this again just for the same issue to occur.
This is account wide, not just limited to the desktop program, but happens on the spotify mobile app and web player.
I can confirm that there are no filters hiding the albums.
I imagine that this is quite frustrating. I doubt that you went past the 10'000 song download limit, or did you? If that's the case, then I think songs will get removed from your library in such a manner as you describe.
If you use social media, you could try reaching out to the SpotifyCares team. You can reach them via Facebook or Twitter.
If you need more assistance, don't hesitate to reply in this thread.