Tracking a phone in Kenya with or without IMEI and expecting to find it is not easy and worth it because thieves have mastered the skill of changing IMEIs. Very few high-end phones can be found. In this case, you need to report to the police that your phone is lost, and go for tracking at the DCI offices.
If the phone was not stolen by a smart thief, DCI can ask Safaricom to keep tacking any number that uses the phone and raise an alarm. This takes time
If you are using a Samsung phone, make sure you create an account and as it will make the tracking process easy.