What should my colleague do who found a mobile phone and was unable to return it to its owner after two failed attempts, then its owner burned the number, knowing that the phone contains materials and numbers of women that might be embarrassing to its owner?

The ruling concerning the aforementioned mobile phone is the ruling on a found item (Luqata). The damage to the SIM card or missing an appointment does not mean it becomes the property of any one person. Rather, it remains the property of its owner. The person who finds it must safeguard it, and he is accountable for it if he disposes of it or is negligent in safeguarding it.