These days, he said, “tracking options are getting fewer” as thieves have got smarter. Now, as soon as they grab a phone from the hands of an unsuspecting individual, they tend to put it into airplane mode or into a metal wire-lined faraday bag which blocks the device’s GPS and phone signal. Less professional thieves wrap them in kitchen foil.
www.londoncentric.media, in "Kitchen foil and Algerian markets: What happens when your phone is stolen in London?"