Indian Railways — theft of mobile

Dear sir,
I was travelling from sambalpur road to kharagpur on 30/07/2017 on train no 18006. Pnr no [protected]. At around 1:00 am i found my mobile missing. I lodged a complaint of missing at grp kharagpur at 5:30 am morning.
The fir no is 0054/17. On 31st evening with the help of mi cloud i got the mobile number of a new sim inserted into my device and also the location. Then using truecaller and facebook i got the name and photo of the person having my device. I rang him and he told he has got my mobile. On the next day morning i informed and submitted all the information i had to the grp kharagpur. How many days the police will take to catch the thief. When everything is clear why dont they catch the thief as soon as possible. I have lost any hope from police. Even i dont know where is the case now. How people without ticket are allowed in the reservation coaches. Police is not doing there work properly.