You really have an obligation to get the buyer to pay you or they are a shirker. They made a contract with ebay to pay for an auction that they won. You made an abligation to ebay to try to get paid to settle the contract. Never heard of sending someone a card, since you have email. If they are not paying up. You are obligated to file with ebay for nonpaying bidder. This usually disloges them into paying.
Maybe you are afraid that they will give you a negative because you tried to get paid for an auction that they won and said they would pay for, but decided they didn't feel like paying for. I tried the waiting just up to the 90 days to catch them just right and it never worked. 90 days is a long time and you will likely forgive them the nonpayment and let them go as myself and others have. Ebay has the system to get paid, its just a matter of using it. I use it all the time now since I got used to simple system it is. I hope this helps.