The jeweller was travelling in New Jalpaiguri-Howrah Down Shatabdi Express.
"The duo tricked the jeweller saying that his bag had been lost when the train stopped at a signal before Jamir Ghata station. The moment he pointed towards his bag, the duo snatched it and deboarded the standing train at around 9.20 am," IC GRP Krishna Gopal Datta said.
The police suspect that the duo followed him from Malda town where he boarded the train to go to Kolkata.