I think you may be talking about the buttons in the bezel surrounding the radio and center AC vents.
It depends on the options you have on your Sport Trac, and some are carry-overs from the regular Explorer models but were never available on the Sport Trac:
If the Trac does not have OEM fog-lights, there will be a button blank there.
If the Trac does not have 4WD it will have a round blank were the 4WD switch would be.
Sport Tracs are not equipped with rear defoggers as Explorers, so you may find a blank button for the rear defrosters go.
If someone added an aftermarket dash trim bezel (wood, carbon fiber, etc), many dash trim kits also fit Explorers and they provide button blanks to fill in where the Sport Trac is missing an Explorer option switch.
Gen-1 Sport Trac's with Seat Heaters will have the switch on the outside of the seat with the other seat controls.
This only applies to the Gen-1 Sport Trac(2001-2006) Gen-2 Sport Trac's are different.
...Rich