Disappearance of horses, armors and bows

During former sessions I experienced the disappearance of horses and armors. Today I played Miecraft in survival mode. I had three bows gained by fishing, kept in the same chest.
The last time I saw them was yesterday. Today I started again and when I wanted to fetch one they weren't there any more. The chest was nearly full with other things, but as far as I can see only the bows were missing.
Strikingly only valuable things seem to be affected by such a loss.
Did I make a mistake, is it natural or part of the game that such things happen or is there a bug?
Made me quite sad that such valued things just vanish.