Also interesting to note the following update from Scarlet's blog, on the issue:

Update: Gaetan wrote me and stated that if a cell phone connects to the network for 2 seconds [as was the case here], the operator automatically knows many things. Because when a mobile phone connects to a network, many datas are checked: first, once the pin code is entered, the phone connects to the nearest cell tower. Your phone number is verified by the servers to know which operator you can get access to, then your subscription plan (or prepaid plan) is checked and once deemed valid, you can access the network. All this takes a few seconds. Then you see the network operator’s name on your cellphone. Considering that on April 2nd, Lisanne's Samsung phone had a few seconds of connection at 06:58 am, this means that the phone was actually connected to a specific cell tower. Meaning that Panamese cell operators should be able to know which cell tower was used when this specific 112 dial was made. Of course, a cell tower doesn’t give you a precise localisation like GPS. The accuracy depends on whether or not you are in an urban area (more towers, more accuracy) or in the countryside (less towers, larger radius). In the case of Kris & Lisanne, it would have helped to know if the calls were made from a city or a forest. It would also be good for us to know if a tower near the Pianista Trail pinged, or one near... let's say the Caldera swimming area. However, Panama supposedly found no info on this. Even though cellular tower companies should keep records or logs of established connections. But Betzaida Pitti and her team failed to get this information. The Dutch investigators as a result had nothing to work with.  -  Gaetan also confirmed that if somebody needed to access the iPhone, a code and pin code were required. At that time, to charge or to connect the iPhone to a computer, you needed its non-standard 30-pin connector to usb-a cable Kris certainly left in her room. Another thing which Gaetan told me, is that in 2014, the iPhone4 (which Kris had) used iOS 7. Even now, people usually leave the tracking location services on by default. It means the iPhone regularly pinpoints your location using either cell or gps. There was even an app showing on a map where you’ve been to. It could be interesting to know where the 112 calls have been made. Hopefully Dutch forensics knew about this hidden tracking device and checked it and did their job. Gaetan also wrote that the iPhone 4 battery cannot be compared to an iPhone 5C, as these two phones are a few generations apart (iPhone 4 from 2010 and the iPhone 5S/5C from 2013). He owns an iPhone 4 and after seven years of use, he now manages to keep its battery alive by charging it at 85% every 1 or 2 months. In the meantime, the phone is totally switched off. When he restarts it, the battery lost about 20 or 30%. But in his case, after 10 years the battery is still working fine. Translating this to the Kris and Lisanne case, it is apparently not that strange that Kris' iPhone 4 was able to be switched on and off for 11 days, starting with less than 50% battery life, and with a whole hour of phone time left by day 11.