What is your backup plan if a phone goes missing during a trip?

A phone can hold the boarding pass, maps, accommodation messages, payment access, and the only copy of a useful contact number. Losing it would interrupt much more than taking photos. That makes a backup plan worth thinking through before there is a problem.

Which small preparations would let you keep going for a day without your usual device? Interested in practical arrangements for getting to accommodation, contacting someone trusted, and accessing essential information. Please describe the method rather than sharing sensitive account recovery details. Also curious about backups that turned out to be too complicated to maintain.