So being tired and an idiot, I left my iPhone 5 in a cab in Boston after arriving around 11pm. Remembered Find My iPhone (though wasn't sure if I even had it activated), so logged in to iCloud with my Mac. Bingo. Tracked cab moving back to airport and sent a 'lost sound' and then put the phone in 'lost mode' (with message of hotel, phone and reward). Shortly thereafter the phone went dark/offline. Probably an existential question, but how long do I wait before giving up on humanity and using the last Find My iPhone option - frying the phone?