For many decades, losing your wallet was clearly the worst. Not only were you suddenly without means to pay for anything, but you had been displaced of much of your personal information and were facing hours and hours of dealing with credit card companies and the DMV. Fun!
These days, a smartphone also packs a significant portion of your life into a small package that you carry with you everywhere and sometimes misplace. It also generally costs more than a wallet. So is the smartphone now the thing you'd least like to escape mysteriously from your pocket?