I've just spent a good hour reading a very detailed blog post about the missing Dutch girls in Panama.
It seems to me that it is being massively over complicated.
The phone calls:
The phones were both used numerous times to call for help, until one day the IPhone stopped being used. Then the battery on the Samsung gave up and there followed many unsuccessful attempts to get access to the iPhone.
It seems likely to me that the iPhone owner had already died, or was incapacitated to a point of unconscious-ness at that point and the Samsung owner was just trying to use their phone.
Much was made that the first phone call was made whilst it was still light when they were probably still on or in sight of the main path. One of the girls may have slipped, fallen or otherwise hurt herself too badly to attempt walking out.
The nighttime photos:
The camera was probably being used in an attempt to signal for help with the flash. The photos of many random things are probably just that. Random things that got in the way of the flash.
The locations of the rucksack and bones:
See attached image taken from the blog. It seems most likely to me that the girls attempted to cross the river on the monkey bridge, got into trouble and fell in the river. The various bones and clothing/accessories washed downstream from there.
Yes, many holes in my theory... most telling being the fact that the rucksack was dry whilst not being a waterproof one and the randomness of the bras having been taken off and out in them.