When I backed out my game for 5 minutes my gold ingots that were in my chest were gone

What I thought would happen was that they would be there when I returned

What actually happened was that there was a space where my gold ingots previously were in the chest I made and so I had lost them and couldn't use them

Steps to Reproduce:
1. Start a survival game and find some gold.
2. Place the gold in a furnace to get gold ingots
3. Place gold ingots in a chest
4. Back out of the game by pressing the home button on your ipad
5. Come back in 5 or so minutes and they will be gone