Buses have to follow their schedule. If you do not have a proper visa in you passport, if you lost your passport on the way, if you spend too much time in the restroom, if you don't have local currency to pay for your visa on arrival, if you get detained by customs or if anything else happens that causes a delay, you can expect the bus to be gone when you get through immigration. Don't waste any time, the bus will leave you behind. It is written in the bus operator's policy. They will take your luggage and keep it at the final destination until you come to pick it up.