If you, in turn, want to be visible to friends upon Facebook mobile number search, ensure that you keep your cell phone number public.
Where to activate Facebook search by phone number
See the screenshot below to navigate to where you can add or remove your Facebook contact number.
To achieve that feature on your Facebook account, do the following:
1. Login Facebook via https://facebook.com
2. Click the V-like icon at the top right corner of your page
3. Select Settings from the drop-down menu
4. Locate and click on the mobile option at the left column of the page that appears
5. Hover about the page that appears and adds your cell phone number in the spaces provided and clicks on the save changes option.
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