u have every single right to ignore the buyer. the buyer and other people might say that u're irresponsible, conman, etc. But based from ur description, it's not ur fault at all. Who knows what the buyer did with the hp. He might even change the phone's LCD to another phone, and then he say the phone u sold was faulty. An educated person will support u if any problem comes up. Others might just bash and flame u... I would strongly suggest that u ignore the buyer. Repairing the LCD wont be cheap u know.