Call the phone and see if it rings, goes straight to voicemail, or says the number is unavailable
Send a text message and check whether it shows delivered or remains undelivered
Try calling at different times to rule out temporary network issues
Check whether the phone appears offline in messaging apps
Look for signs that the phone is not reachable, such as no response to calls, texts, or app messages
Ask the person through another contact method if their phone is off or dead
If you have permission, use a phone-finding or device-sharing app to check the device status
Notice whether repeated attempts always fail across calls, texts, and apps
Consider that a dead battery, no service, airplane mode, or a powered-off phone can all look similar