I went to the PHX counter and presented the card in person to ticket a reservation. The card is in perfect condition with the exception of the missing digits. The agent swiped the card satisfactorily, however WNs computer requires manual entry of the four digits. The agent was not able to read the numbers off the card and therefore would not redeem the card value per company policy.

So at this point it looks like I have a worthless piece of plastic and Southwest Airlines is keeping my money.