I received my nephew's on tourist visa on site yesterday as no other channel was available and the immigration staff said "bring this if he will need any extension". A sine qua non.
most probably the airline will turn him back. happened to people visiting. had to get an emergency passport next day, lucky it was a weekday. costs extra too. if in your city you will not have to pay for hotels. if there is a flight to be put on the next day. if ticket is re-bookable or ticket lost.