Bummer. Hopefully someone will turn them in to Lost & Found and the bus operator (metro, private, whatever) will contact you. Make sure you contact the owner/operator of the bus. They might already have them.
Or, a dishonest person may take advantage of your misfortune. You might start checking local sales channels, like (here in the US) Craigslist, eBay, etc...whatever you have where you are. Maybe take out an announcement and offer a reward.
As far as accessing your data, the typical person probably can't easily do it if your laptop is password protected, but it all depends on the brand/OS....and very much the skill level of the person who has it, or if they know someone. Just about anything can be broken with the right tools and skills. Unless you've employed multiple layers and destructive consequences for repeated failures (not common) yes, your data can be accessed.
If it's Apple, do you have the "Find My" enabled? Others may have something similar but I'v e been Mac since 2007 and left M$ with Vista.