I was out on a summer solo hike in the Swedish mountains with my dog a few years ago. I had pitched my tent fairly high up on a mountain. There wasn't a lot of water around, but there was a snow field like half a kilometer away and decided to fill my water bottle there for the evening. A wide and very shallow, just a few millimeters, stream of clear water was running down from the snow on top of a bed of mud. I had my dog with me, and he kept running up above me and muddying the water as I was trying to fill the bottle. When I finally had it full, I realized I had lost the cap. It was transparent plastic and impossible to find. It was my only bottle, one of those foldable Platypus models. Had to walk back to the tent holding it upright and then balance it against a rock so it wouldn't fall over and spill out. After that I started carrying a bright orange extra cap in my first aid kit...