I've never seen this before. I didn't do anything different, just went on, played, the next day, the world I was playing is gone. Anyone experience this before? When I check my saves, I see the world still there, so it's just not loading.

Here's a Log, just in case you need it.
http://paste.feed-the-beast.com/view/3253fa95

Looks like an issue with the level.dat

Can you try to rename ore move both level.dat files out of your singleplayer world folder and see what happens?

[20:13:20] [Client thread/ERROR]: Exception reading C:\Users\Ve Nguyen\Documents\Material energy\GalacticScience\minecraft\saves\Third World, 1st of Observatory\level.dat
java.util.zip.ZipException: Not in GZIP format

All right, modpack loading up now. You guys work hard to respond quickly. Is it like notified on your phone?
I moved the level.dat files (the old and new one) out into the saves folder. Let's see what happens.

I get an email and a notification on our community chat

I see. So I could spam a billion times to fill up your E-Mail XD (then you guys would mute me or something) ( ͡° ͜ʖ ͡°)

Edit: Does editing a comment also gives an email and a notification?

Back, and the world is still missing. Here's the log (Note: still contains the log from original post)
http://paste.feed-the-beast.com/view/f7ebf086

Now, I will restart the launcher and thus refresh the console log.

Okay, can you undo your level.dat change and upload the world? I will look later if I can fix the world.

How do I upload the world?

Also while you are replying, I will try to put in only the new level.dat file.

Zip it and upload it to dropbox, mediafire or something like this

You maybe can also upload it here if you drag and drop it into the text box

Ah, when I compress it it turns it into a WinRaR zip, and thats not accepted!

Ima just download to dropbox, here and now.
And also download dropbox.

Sorry @SirWilli, but I have to go to sleep for the night. Great modpack, (and changed configs, XD) and I will get back to you in...18 hours?

Alright

before I go to bed. I finally got it:
https://www.dropbox.com/sh/y8lsl3z572p5bmf/AADqKcxlEO6qA9dN9bZjJTipa?dl=0

Hello, just a quick update before I get to school, the singleplayer world appears, but when I try to load up the world, it crashes and I am back to the launcher. Also with that level.dat file, I had replaced the other level.dat file.
Here's the log:
http://paste.feed-the-beast.com/view/755ce9fd

Your questing data seems to be corrupted too. You have to delete the players.dat in the HardcoreQuesting folder. You can try if the backup works.

Ok, got an fix for you. Go into the maps/Observatory folder in your modpack directory and copy the level.dat then paste it in your world folder.

All right, world loaded up, but now I am in the void.

I heard there was a command to get back to the moon in the exact spot needed.

Man, I wonder what caused all this. Welp, time to fix files, go eat, bathroom, all that jazzy jazz.

Man, all you guys are awesome. Diligently working on a modpack that I am addicted to (in fact, more addicted than the material energy series, and thats ALOT) I wish I could donate but sadly I am not of age of which I can do such a thing.

@Geekerandy the level.dat contains the information on which item ID does have which item name. As your old level.dat had different data it turned them into tnt but as long as there are not too many blocks you should be fine replacing them in creative mode.

Found it. On this:
http://forum.feed-the-beast.com/threads/1-7-10-hqm-survival-galactic-science-something-fresh.86203/page-41

/cofh tpx -28.

Welp, I come back the moon using that command, and I spawn next to a space lander. Looks like everything is intact, my base is nowhere in sight.

I used the coordinates of a different world I had, open to LAN and to the coords, and everything looks normal. So the solution to the problem is to delete the player.dat file in the HardcoreQuesting file. Welp, time to close this now. Thank you for everything! P.S, I lost all my player progress because I deleted the player.dat file. Oh well, /hqm edit mode!

ONE LAST NOTE! All um cough XU generators cough Changed configs cough turned into TNT from the Dalek Mod. Must be a consequence or something.

Edit: Also a x64 lava generator (cheated in, so what?) turned into a oxidizer. Accidentally breaking it in creative mode caused a crash. But I am sure there is no harm at all, just like accidently pressing a number and esc while inside a golden bag of holding at the same time just creates a weird crash, probably unfixable.

Edit #2: Welp, I stored everything I had into golden bags, and now I lost it all from death in the overworld. I might as well start a new world, or spawn in a billion items to fix my power station (dalek tnt, I hate you).

Ah, I see. Thank you for that. Welp, I can replace everything with creative