It did really suck ._. because of that, I went to bed 2.5 hours later than I intended to, crap. >.< :P I did manage to rebuild everything in 20-30 minutes, though, and everything appears to be working, so that is great. :D
I know what caused it too: I accidentally logged into the world I was working in with my alt. From that point on, it stopped saving the chunks... -_- it was really weird, I went into a minecart away from where I was working, and immediately back, and then everything was gone... Quite odd.
So, if you ever accidentally log into a world you're already working on in another client, leave the world on both clients immediately, and you should be fine. :)
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