Lesson number one when camping with water bottles. If you use them for dousing the camp fire just before bed (an act best performed in total darkness for effect) don't leave them open and empty on the picnic table.
The following morning I filled one of the bottles and took it and several chocolate chip cookies down to the lake shore early (before my solitary explore and mountain climb while everyone else still slept) and drank several relaxing swallows on the dock before I noticed this.
I gave it a lecture and then lowered a twig to let it climb out. Silly thing.