Diamonds Have Disapered!!!

I found 11 diamonds. I brought them to my house. I used 3 to make a diamond pickaxe. I put the remaining 8 in a chest and shut down midnecraft. I come back the next day and the diamond pickaxe, my 8 diamonds and 63 pieces of redstone are gone. I go and mine 5 pieces of diamonds and shut down minecraft shortly after that. I log on today (a week later) and my redstone (63 pieces) are back, but my 5 diamonds have disapered, and the 8 diamonds and the diamond pickaxe is still missing. I did not die and lose them that way. Please fix this bug so that I can keep my mined diamonds!