Back in the day, my first mobile phone got stolen from my coat at work.
Didn’t make a big fuss about it as it gave me a reason to get a better phone.
As for precautions, the iCloud lock from Apple is the best way to prevent people from stealing Apple devices. They can’t use it, safe for selling it for pieces of hardware.
It goes without saying that you shouldn’t show where you keep your phone if you don’t want to encourage people to pickpocket you.