I’ve been hiking and climbing in the US wilderness for years and always been leaving my stuff without supervision. I’m more careful when camping in campgrounds, though. However, I’ve never had any problem with loosing anything till the last summer.
While descending Mt Rainier I stopped at Camp Muir (at about 10,500 feet) to rest, eat, and prepare some water for the rest of the route to the parking lot (at about 5,500 feet). After melting the snow and boiling the water, I placed the bottles in the snow near by my backpack. Just before I was ready to hit down I went to the restroom for a minute or two and after came back my bottles were gone. I spent almost 30 minuets looking and asking around. No luck. To help me, one person gave me an empty 1-gallon container. On my way down I catch up with a nice couple I met at the camp, and after telling the story they immediately offered me splitting their water.
I always get dehydrated on my way down; that day was extremely hot, which made even worse. Thanks to the couple I was OK, but still cannot believe what happened that day. It seems some people follow no CODE and no ethics. Fortunately, it happened on my way down.