Immediately prefer a complaint with RPF as well as the Railway authorities. Inform your mobile service provider. If IMEI number is available it could easily be traced. I hope there is a possibility of the attendant handing over the instrument to the supervisor and you will get it back. If you get back, please do not forget to recognise the honesty and give due appreciation for the same in the proper forum. It is much more valuable than monetary reward. Please do not forget to post your experience here.