Solution1: Use the Apple IOS “Find My Friends” app or Android “Friend Location” app to check their location. They may be in an unexpected location.
Solution 2: Use the Apple IOS “Find My Phone” app or the Android “Find Device” app to ring their phone even if it’s on mute.
This will work ONLY if you are on the same cell phone plan
How to get it: Apple App Store or Google Playstore
How it works: If you have different types of phones, the IOS/Android app Life 360 will work for Solution 1