If you just have lost your mobile phone, you can only hope that someone who has found it would be in attitude for returning its back to you. You could call out as Del said in hope to converse with this person.
If mobile had been stolen it's likely to be of 100% probability your sim had been already removed . Theoretically here is a small room to track where it's located by its IMEI when your former mobile receives rings either rings out itself. It depends on what's a policy employed for this kind of crimes in India. Why don't you go to nearest police station? Of course if you've not any documents for stolen/lost phone --- here is not a chance.
In any case you mobile operator has to recover your sim card.
Get the police to ring the number and offer to buy the car that has been advertised.
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