1. Create a new local game
2. Send stuff to a friend (with mailbox)
3. Close the D3 application (from PS menu)
4. Relaunch the game. Notice that your items are still in your inventory.
5. Profit !
How ? : Because it didn't save your local game.
Why ? : Force quitting the game by closing the application from PS menu does not save your game but your friend still retain sent items.