Embedded controler applications often have multiplexed keypads, there is a common for every row and a common for every column, the micro scans the pad to see which if any button has been pressed.
Being only a 6 button pad you might be lucky and each button may have its own connection to the micro and have a common ground, check the traces, the unit may still have a multiplexed keypad, esp if the same software is used on other products which is often the case.