While I was working on my mining tunnel my enchanted iron pick axe broke. It had 3 enchantments (Unbreaking III or IV, Efficiency III, Silk Touch) I decided to drag and drop my next enchanted iron pick axe (Unbreaking III) to replace it on the hot bar.

Once I clicked and dragged the back up pick axe to the #2 space on the hot bar to my surprise my pick axe that just broke popped out on the ground in front of me. I picked it up and it was at 0 durability, couple swings and it broke again. Same thing happened, clicked and dragged the new pick axe (it was slightly damaged) and it respawned my old one that had just broken.

I was able to get it to do this a few times before I just went back to what I was doing. Later after I depleted the durability of my second pick axe I was returning to my mine camp and ate some steak, to my surprise the second pickaxe (unbreaking III) popped out of me and I picked it back up.

Seems to be some kind of item dupe or restore happening. I haven't had it happen anywhere else or any other time since I've been playing after the 1.9 update. It's not really game breaking since the items respawn with next to no durability but I thought I'd report it anyways.