Crack in inner LCD screen of iPhone 4 or not

Yesterday, I suddenly realized that there was a small clump of red, green and black lines appearing on the top left hand corner of my iPhone screen (near to the receptioon signal). When I went to the Apple Service Centre, I was told that there was a crack in the inner LCD screen which led to it. He even pointed that the fine green line is an indication of a cracked LCD and it will only get worse in the long run. However, over yesterday's night and today, this "clump" has started to slowly disappeared and now it is totally gone. I am totally confused? Is it a cracked LCD or some weird problem? Is there anyone who can shed some light on what is going on? Although I'm happy that it is gone and things seems to return to normal.