AHHH GOD just fell into the lava. Lost some diamond and lots of materials.....oh god oh god.
In hate it when that happens. In the very first world I created, I managed to stumble onto a large cave system beneath my home and followed it down to a bunch of lava. To even reach the lava, I had to destroy a Zombie Spawner - which netted me a Music Disk, a Pig Saddle, and a bunch of iron that I was quite happy to receive - before stumbling onto a wide cavern filled with lava. Much to my happiness, I also stumbled onto a vein of diamond, along with a few scattered bits here and there. I had over 20 diamond in hand when I went after a small batch of coal of all things... And stumbled into a little one-square wide crevice I hadn't noticed. Filled with lava.
Lost the Music Disk, saddle, a ton of iron, all my Diamonds, a set of Iron tools, about a dozen blocks of gold...
I destroyed the world in a rage and started up a new one. That little batch of lava started the cataclysm. xD
EDIT: Also, I've decided on the first thing I'm going to do upon receiving that file, should it not be done already... Fill up that cursed sign chest with signs. Opened it up earlier to mark something in my private copy of the world - which I'm just exploring and planning in - and discovered it was completely empty. Disappointing. D: