Yup!!! Finally going back to home. No trace of that cell yet. Call it spread of technology, many people have gotten smart. Might be someone met him or the changed SIM, he placed into cell has no GPRS into it. So, not able to trace him. But will mention again that if there was Google Lattitude in this Nokia N900 then I was able to do something in time.
Still have not reported the theft complaint as giving time to the person to make some mistake though you can understand that less chances by now.
For those, who care, mentioning the IMEI number here