You probably have accounts on different websites or apps where you used your phone number to sign up. Having access to your phone means, the intruder can reset the passwords to gain unauthorized access to your accounts. The result will be far more severe if you keep your debit/credit card added in your account- prompting the intruder to make transactions.
We often use a digital wallet, most of which can be unlocked with your phone number using the simple “Forgot Password” method – facilitating the intruder to empty your wallet. He may even gain access to your bank account.
Moreover, your phone may contain sensitive notes, private pictures or apps you remained logged in.
Set up a remote data-wipe facility. This is very handy to format your mobile from remote.
If you lose your phone, block your number as soon as possible. Lock your phone with a pattern or password. Also, protect individual sensitive apps like email, gallery, settings etc. with an app lock. Don’t save your card in any app.