MacBook Pro :: Ghost Mark On Screen

For sometime now i have got this ghost mark on my macbook pro's screen. I did book an appointment at apple and showed someone at the genus bar but at the time he said it was just due to the keyboard pressing against the screen and if i cleaned it well it would go away. In saying this i had to buy this cleaning kit which he said would do the job. At the time in the apple store it did seem to fade but i now feel that was just due to the stores lighting. I still have the mark months later and its still as obvious as it was before. I was wondering if you guys have any advise on how to get rid. I only see it when its dark and there is black on the screen and though it doesnt bother me that much in a few weeks im selling this and would prefer to have the problem fixed. i did do some research and didnt find much, only thing i did find was about replacing the screen and i cannot do that due to time and money and am sure there is a easier way. i have attached a photo trying to show the ghost mark (in the black box) but because i took it on my iphone it doesnt show well.