Hello Ckoumophau99
Please report the loss immediately to SBB, if the laptop was found by the staff, it will be sent to the SBB Lost & Found office:
https://www.sbb.ch/en/help-and-contact/lost-found-office/submit-loss-report.html#anchor1
Please, also inform the local police in Montreux about the loss, as well as the Indian embassy in Switzerland:
https://www.indembassybern.gov.in/
Best regards,
Roland
Ps: there would have been the option to start an emergency search request for lost items, possible for IC/IR trains (with train attendants on board), as long as the trains has not completed its journey.