My friend grows and kills his own food, it's not massively difficult and when pushed, people are perfectly capable of it. We are not completely dependant upon electronics. At the source, people only need other people. The world has always been a playground. It's harder, but not impossible. As for fire... we could go all castaway on it. Freezing in winter is... debatable and depends where you are. In england, you would not freeze to death if you have enough clothes, though older people will die and so will kids, but that's what it's like when you step back an era.
Oh and the cannibals are notoriously unmotivated. They wont exactly search much, just shuffle around a bit really, until they notice someone going past.