It's also likely that the electrosensitives have had this test run on them so many times by ordinary people where "I'll just hide this radio device here somewhe

It's also likely that the electrosensitives have had this test run on them so many times by ordinary people where "I'll just hide this radio device here somewhere and see if they pick it up", that they get attuned to finding out the hidden object, rather than actual sensitivity. It would have been more amusing if he had the phone switched off already or no phone at all and they asked him to switch it off.