To prevent losing your items, or even worse – having them stolen in Minecraft PE, use the Lockable Chests modification. The author approached the creation of the mod very responsibly.
Features of Lockable Chests Mod
In Minecraft, a chest like this will appear. It cannot be broken, “mined,” or opened. The /kill command won’t work. However, you can do it using two items – a key card of the corresponding color or a recognizer. You can change the color of the textures using dyes.
Key card. Recolor it in Minecraft to match the color of the icon on the chest to unlock it.
Recognizer. Just in case, so that no one else crafts key maps in the game, you can use this thing. No one but you will be able to unlock the chest.
Special scissors. Since chests in Minecraft BE will become indestructible, you will need an item that can break them when needed. Only the player who created the chest can use such scissors on it. Any other user will just waste their time.
To make the mod work correctly, be sure to enable experimental gameplay features.