first this issue seems to happen in both 1.4.6 and 1.4.7.. this issue happened to me yesterday.. in the last 24 hours i've had to remake my diamond foot armor because it gets deleted.. the first way that it happened was i held the q key in by accident and i dropped my diamond sword.. when i picked my sword up it didn't go in my empty hotbar slot or my inventory.. it went in my foot armor slot deleting my foot armor and my sword was in it's place and that's happened twice.. today all i did was pick up an egg from one of my chickens and it went automaticly into my foot armor slot and for the 4th time my diamond foot armor got deleted and an egg was in it's place.. i play on my own server and i switched servers recently.. u used to use the normal minecraft server but since there's no plugins and i wanted things to be protected i went with the bukkit server.. but they don't update their stuff enough so i imported everything back to the original server so we could all use 1.4.7