Corrupt World File...?

When I opened my single player survival world I was standing in the same place I left it last time; however my inventory was empty. Also any chests in my house were empty and all paintings and item frames had popped of the wall (in the case of the item frames, losing the item inside). Furthermore, any redstone circuits had frozen and needed a block update to continue. When I travelled a bit further, any chests further away (my brother plays on it through LAN world sometimes) had not been emptied. Could this be something to do with them being in unloaded chunks?
Do you know what has happened here, how I can avoid it happening again, and whether this can be undone?
Thanks.