This is where one time codes that you keep in your wallet come in. Many second factor auth systems use this. There is a list of 10 codes that can be used once

This is where one time codes that you keep in your wallet come in. Many second factor auth systems use this. There is a list of 10 codes that can be used once each (and they're only valid used in order, so only one is valid at a time). You print this list out and keep it in your wallet or wherever else in case you lose your phone. If you lose both your phone and this list, then you are in fact screwed.