Out of experience (been lost on many cities around the world). You get lost, have money with you... no problem, you can always catch a cab... or borrow a phone!
Phone.. then I could call for someone to come get me... after I google mapped myself to find were I was... then I would go online and kill my ATM Card, and order one to be picked up at the nearest bank. Then a call to the DMV to start the process of replacing my ID.
So I can call somebody to come get me or get directions from someone. I could also call for a cab to come get me, and then pay them once I get home. My wallet won't help me, although it would be nice to have both at the same time.
the wallet would have (maybe) some money in it (not much) and a credit/debit card, and with the card i could get a hotel room, something to eat, maybe a train/bus/plane ticket back to wherever i belonged. with only a phone, i could call somebody and cry but that's about it,
with a phone you call the police or somthing to help you become home