Your child might be using WhatsApp on the laptop or PC via the browser or the desktop app, but the messaging platform only works when the primary device, in this case, the smartphone, is connected to the internet and is turned on. So, if he loses his phone or it gets stolen, he will not be able to use the messaging app anywhere else.
WhatsApp has mentioned a few steps that can be followed if a smartphone is lost or stolen in order to stop other people from being able to access your WhatsApp account. Remote deactivation of the WhatsApp account is not possible so make sure your kid follows these steps.
STEPS TO FOLLOW
1. First things first. Help your child lock his SIM card. For this, you need to call your network provider and get them to lock it. How does this help? Locking SIM card makes it impossible to verify the connected WhatsApp account on that phone again since this device will no longer be able to receive SMSs or calls for verification.
2. Once the SIM is locked, your child can use a new SIM card with the same number to activate her WhatsApp on a new phone. This is the easiest and fastest way to deactivate an account on the stolen/lost device since WhatsApp can only be activated with one phone number one device at a time.
3. The second option is to deactivate the WhatsApp account without the SIM card. For that an email needs to be sent to WhatsApp with the phrase “Lost/Stolen: Please deactivate my account" in the body of the email. Make sure the phone number is included in full international format. One needs to use +91 as a prefix for Indian numbers.
4. Once the account is deactivated, all the WhatsApp contacts on your child's phone can still see his profile and send him messages. This will remain “pending” for up to 30 days. If the account is reactivates within 30 days, he will receive all the messages and will still be a part of all the WhatsApp groups. If the account cannot be activated within 30 days, it will be entirely deleted.
If your child's SIM card is locked, she can still use WhatsApp with WiFi connection if her WhatsApp account hasn't been deactivated. However, this should be done only if the device is recovered and SIM is deactivated. This method of using WhatsApp on WiFi is only a temporary solution. One can use it this way as a stop-gap till he or she doesn’t get a new device or reactivates the SIM.
Also, if all the WhatsApp data has been backed up on Google Drive, iCloud, or OneDrive before the phone was lost or stolen, then it will be possible to recover the chat history and all media.