Look closely, very last set of doors at the back of the bus, under the right side door, you'll see the one tire.
Vehicles need more ground clearance than that:
Vehicles need more ground clearance than that. What happens when 60 pax board it? It grounds!
Again, if the airport has slightly raised ground polygons to prevent flickering, they might be more difficult to see than they usually are.
This is the real life vehicle featured in GSX ( Neoplan airport bus )https://www.everypixel.com/image-473344793757047131As you can see, even in real life, wheels are quite hard to see due to its design.
Captain Kevin, I would still expect to see the wheels on a bus.