Losing a smartphone can be stressful, especially because it may contain personal photos, banking apps, private conversations, documents and access to your online accounts.

But losing the physical device doesn't necessarily mean losing control of your data. If you act quickly, several built-in security features can help protect your information.

1. Try to Locate the Phone Immediately

Use the device-finding service connected to your phone.

For Android devices, Google's Find Hub can help locate, secure or erase a supported device. On iPhones, Apple's Find My service provides similar options.

If the phone is nearby, you may also be able to make it play a sound.

2. Lock the Device Remotely

If you cannot recover the phone immediately, remotely lock it.

A strong screen lock is one of your most important lines of defence because it can prevent someone from easily accessing your apps, photographs and messages.

If your phone supports a remote-lock feature, use it as soon as possible.

3. Display a Contact Number

Some device-finding services allow you to display a message or phone number on the lock screen.

You can write something simple such as:

"Phone lost. Please call this number."

This gives an honest finder a way to contact you without giving them access to your phone.

4. Contact Your Mobile Operator

Your SIM card can potentially be misused if someone gains access to it.

Contact your mobile network provider and ask them to suspend the SIM or issue a replacement, particularly if you believe the phone has been stolen.

This can also help prevent unauthorized use of your mobile number.

5. Secure Your Important Accounts

If you believe someone may have accessed your phone, change passwords for your most important accounts.

Start with your email account because email is often used to reset passwords for other services.

Then review important financial, social-media and cloud-storage accounts.

6. Contact Your Bank if Necessary

If your phone contains banking or payment applications and you suspect someone may be able to access them, contact your bank immediately.

You can ask the bank what steps are appropriate for securing mobile banking and payment services associated with the lost device.

Don't wait if you notice an unfamiliar transaction.

7. Don't Go Looking for a Stolen Phone Yourself

If the location service shows your phone at an unfamiliar address or another potentially dangerous location, don't confront anyone yourself.

If you believe the phone has been stolen, provide the location information to the police or appropriate authorities.

Your personal safety is more important than recovering a device.

What If You Can't Recover It?

If you've tried everything and believe the phone is permanently lost, a remote erase may be an option.

However, remember that erasing a device can affect your ability to continue tracking it, depending on the platform and circumstances. Use this option carefully and consider whether you have already exhausted the possibility of recovering the phone.

The Best Protection Starts Before You Lose It

The easiest way to deal with a lost phone is to prepare before it happens.

Keep a strong screen lock enabled, turn on your device-finding service, maintain current backups and make sure you know how to remotely lock your device.

You may never need these features.

But if your phone disappears, knowing exactly what to do in the first few minutes can make a huge difference.