It used to be that the PPV stuff would be added to your card inside of your receiver. Then during the nightly call, it would update your account by sending in the PPV events that you ordered. So if you didn't/don't have a phone line, the items should queue up on the card. The queue is only so big however, and when it's full you will no longer be able to order any more PPV until the receiver is able to complete a call to DirecTV.
I can't remember the size of the queue, but I thought it was around 5-10 items.