I was mining and there were a lot of mobs. My armor was low and when a skeleton shot me my armor died. I then realized my sword was missing. I tested this again and the same thing occurred. It does not matter which piece of armor breaks or wether or not the item has a damage value.

What I expected to happen was the armor would break and my item would still be in my hand.

What actually happened was the armor did break, but the item I was holding disappeared.

Steps to reproduce:
1. Put on armor and hold an Item
2. Take damage until the armor breaks
3. Notice the item that was in your hand is no longer there and has vanished