this kind of thing has waned in and out of favour in a few markets for a few different purposes, ticket booking, hotel rooms in japan too i recall, all barcodes are are a series of numbers in machine scanable form, and anyone promoting the technology for "important" purposes such as this will allow for these numbers to be input manually should scanning fail for any reason, just like if your cornflakes dont scan in tesco the cashier can take two seconds longer and manually input the number. however if you feel the need to be prepared then by all means insist on scanning your phone at the checkout til it works! :P