You are not missing them per se, they should be open unless you plan on fording water.
Use NAPA #704-1361
A nice little drain plug with a plastic gasket. Works perfectly as a wading plug.
M14x1.5 if you want a bolt (but the NAPA plug is better)
"The most unreliable car in the world is the most reliable car in the world." -Jeremy Clarkson refering to the Range Rover