I’ve memorized my credit card details for a decade and a half for pretty much this reason. I don’t often forget my wallet, but it has happened. The few times it has, cashiers have been confused but generally managed to make it work when I’ve given them the numbers. (And to be clear, I’m grateful to them for accommodating the situation.)

I’ve never considered physically embodying cash within my phone. I’m super paranoid about leaving it behind ever since I broke my ankle and had to call my wife to save me, so I’m less likely to forget it than I am my wallet. Thanks for the idea!