That’s a great question that I don’t know the answer to. If the idea is that current from the strike travels across the ground and then into you to complete a circuit, stopping your heart or in less severe cases causing you serious shock, there’s a good chance a phone in your pocket would remain completely outside the circuit (why jump to a phone in a pocket when your body provides an adequate path?) and remain functional and unscathed.
For those who’ve never seen how ground current from a nearby lightning bolt can drop you instantly, I’m attaching a famous video of a soccer game where a lightning strike hit the field and its ground current electrocuted several players.
TRIGGER WARNING:
No player or person died in this incident. They all recovered to varying extents after medical treatment. However, some of the video may be upsetting or disturbing to the viewer, and it’s age restricted. One player can be seen still twitching immediately after the strike, and they are all obviously in pain and distress while medics are actively trying to revive them.