I would think the cell phone would become harmless if you just pull the battery.
I think that some folks here didn't quite get the intent of the 72 hour kit - at that is as a means to get you home or to a place of relative safety in the event of... difficulties. All it would take is the announcement of a 'bank holiday' - which would in short order turn into a holiday from hell. You'd have about an hour before things began to get unpleasant.
Here's the thing - we thought a lot of this through some time ago. That's one of the principal reasons we pulled up stakes and moved to our present home in the Inland Northwest. Why stay around a urban area where people will turn one one another like Kilkenny cats once the toilet paper and the potato chips stop rolling? Why stay in an area where it's all too easy to find yourself herded into a situation by others who don't necessarily have your best interests at heart?
A fighting chance is better than no chance. A wise man prepares...