Items disappear

I happened upon an upper ground mineshaft and began digging it. (I'm in survival mode btw) after around 6 hours of on and off playing I have collected a good sum of red stone, gold, and diamonds. Seeing that I did not have a chest to store the, back at my home I made one. I put it next to some other chests and put the redstone, gold, and diamonds in there. I had roughly 13 diamonds. Anyways I leave to go search the world and after 4 hours of discovering my world I come back to that chest missing with everything that was inside it gone and the trees I had planted outside my house before I left to also be gone. I've also recently seen how I will dig blocks but even though I collect them they are still there. When I walk into em I can see the entire world(see attached photo). Please help