someone stole my stuff!

I came back from my mine and put my stuff in my chest. Then i left.When i logged back on my stuff was gone.I asked an admin (momotoman) and he said that he saw lil lazy opening my chest!I had 30 diamonds,10 lapis lazuli, 3 stacks of redstone, 1 stack of iron, 2 stacks of coal, 23 gold ore, 1 brewing stand and 1 stack of blaze powder