As Ben Blank said, the only thing that will spontaneously cause an explosion, if you haven't made any TNT, is a creeper that got into your house. I see three possible directions for the creeper to enter from:
The caves
Most likely, either you have an insufficiently lit patch of floor in the connected caves (walls and ceilings don't matter), or there is a dark branch that you haven't found. I strongly recommend always installing doors at connections between caves and living space.
The front door
The damage you described seems to be focused around the doorward side of you. You say you removed "the bricks leading up to the door", but if there is still a one-block-jump path it is possible a creeper got in anyway. Next time, don't worry about removing the path, just close the door!
If you have a wooden door, zombies can break them - this will cause a loud sound of someone punching some wood.
The ceiling
You haven't said anything about your ceiling design. Is it possible that your ceiling had a hole in it through which a creeper entered? There are [minimal spoilers] ways for dirt/grass blocks to go away, so if you had a dirt roof perhaps a creeper fell in.
Miscellany
To my surprise, it appeared that nearly all my objects were still there. Most were sitting in the same spot that their chest was in. As best I can tell, I was able to recover nearly everything, with the exception of the signs and 2 of the 5 chest blocks.
Chests drop their contents when destroyed, as you saw. If there had been two explosions, then the second one would have destroyed all of your resources, as they have almost no “health”.
They also tend to leave big craters, and there seemed to be too little structural damage in this case.
The size of an explosion crater depends on the strength of the materials. If you meet a creeper outside, then it will leave a large hole in the dirt, but the same explosion will do much less damage to stone.
Oddly, the door and torches outside were gone, but the structure itself was untouched save for two holes in the floor (marked "Gone" in the above picture).
Wooden objects are generally weaker against explosions, and torches have no blast resistance at all.
I was able to talk about my problem to the Creator of the linked Video above myself via Teamspeak.
Here are some things to keep in mind when building a huge farm like that:
- You absolutely need to clear out a HUGE perimeter around the farm to make sure mobs can only spawn in the area you want them to spawn.
- The perimeter around the farm needs to be 128x128. In my case i only cleared out like 50x50 which is by far not enough and the main reason i got extremly low spawn rates compared to JL's video.
- In MC 1.7 and before it is extremly important to notice that the LC Value (as seen in the debug screen) has a huge impact on the farm and spawning behaviour. The LC Value saves for the given chunk how huge the player has builded in this chunk ever since creation of the chunk. For example you go in newly generated terrain at Y = 50 the LC Value will be 50. If you build a 10 high tower on that place the LC will go up to 60. Note that to have good spawning behaviour your LC value needs to be as low as possible.
- Explanation why the LC Value needs to be as low as possible: When MC trys to spawn a Mob in a given chunk, it only will try to spawn it in the area of the chunk under the LC Value. So, if there are several chunks around your farm with a high LC Value, the higher the chance is, that mobs outside of your farm will spawn, because the given chunk actually has more blocks to spawn mobs upon.
- There also is a mobcap on each MC server. So, if you are alone on the server the complete Mobcap will only be taken by you. If there are more players on the server and they even are in different regions, than statistically each player would get halve of the mobcap which means getting halve of the mobspawns.
- There also is a possibility that mobs will be spawned at the edge of the 128x128 perimeter and not despawn instantly due to a bug / feature. JL told me that when a mob is spawned directly at the edge of the 128x128 perimeter and it touches the end of the render distance the game will put this mob into a "sleep" mode thus stopping rendering it. This however causes the mob to still count to the server mobcap while not despawning. Which means it lowers your spawn rate.
This are the reasons i remember, actually JL has told me far more. I convinced him to post a video on that topic on youtube and explane the topic far more in details. The video will come soon from him.
Hope this helps somebody.
Best Answer
It appears the amount of experience lost upon dying is approximately the same as the amount of orbs that gets dropped.
Upon testing it myself, it seems the experience dropped isn't equal to the experience you had before you died. After running three tests, I usually got about 1/2 of the experience I had before I died.
This image contains three tests: the experience meter before is on top and the experience bar after is below. Also, in the third test, I had an entire bar of experience plus what is shown.