May I know why do you say there is no selector for the radio button? Is PAD not able to detect the UI element?
If not able to get the UI element using normal ways, record the action of just clicking the button, go to the UI elements tab there you will see the element.
Then use this element in the "Get details of element on web page" action.
Get the Value and check what value does it return 0, -1, 1, true, false, etc and accordingly check the status.