there's also the aspect to the issue in the the mobile phone is actually a mobile phone and not a bomb, dildo or any other sundry device.
so the crew can ignore bugger off down route with the phone and let admin return the phone to the owner or dump it in lost property, while the owner may or may not be standing in the terminal at an unmanned desk with a website address to refer to for assistance.
or drop the phone into the hands of ground crew who can return it to the terminal building where the owner may be waiting, or if not return it to where he or she deplaned. rather than taxi the plane down the runway, back down the taxi way to the terminal to the stand, open the door at the jet way and hand the phone to someone else, providing the operator with additional costs, maybe a missed slot into the destination airport intended, the potential of having to deal with pax that have missed onward connections etc etc.
As contacted opined:
Aviation Security, despite best intentions, often lacks one basic element, Common Sense. We are becoming conditioned into irrational behaviour by fear and incorrect application of unworkable procedures.
and the costs for these unworkable practises are being met by the carriers which, in a highly competitive market eats into the profit margins day in, day out, which then has effect on the T&C's and working conditions that we all have to deal with.