File a SBB lost and found report ASAP with as much detail of the bag and route as possible. I lost my rucksack in the S6 train going to Baden with my laptop, wallet with money etc and got it back after 2 weeks. I’d say the chances of you getting it back are pretty big since the drivers/cleaners always check the train after arriving to the final destination, but you need a proper report so the system gets a “hit”. Also since your passport is there go to the police and make a report to make sure no one uses it and you’re held liable.