Enchanted diamond armor disappearing on Hardcore Survival

Put the summary of the bug you're having here

What I expected to happen was...:
To put my newly enchanted diamond armor in a chest to use later.

What actually happened was...:
...but I logged on a day later and it was not in the chest that I left it in.

Steps to Reproduce:*
1. Gather some diamonds from the desert temples ( I used the seed: 1)
2. Gain experience to level 30 and create a diamond chestplate.
3. Enchant diamond chestplate (I recieved enchants prot 3 and thorns 2)
and place into a chest and log out.