This exact same thing happened to me I used the macbook at 7am in the morning, it sat on my couch without anyone home or in contact with it. I came back to it 2.5 hours later, opened it to find the lcd broken and 1/5 of my screen black with lines running thorugh it and with what looks like 2 hairline cracks in the bottom left corner in an area that is impossible to come in contact with from dropping or anything other than jabbing with a stick...or something absurd!
It wasn't shut aggressively, in contact with anything or anything wedged between it, nor did anyone come in contact with it, i.e. no source of impact.
I jwaited a week to get in to see someone for an appointment at the Genius Bar to be told this is accidental damage and not covered by the warranty or Apple Care. The macbook is a refurbished product, purchased through the apple website and I have had it for 5 months. I am beyond unhappy with this entire experience. I am expected to pay out of pocket for repairs, which cost 1/3 of waht I paid for the item 5 months ago new. I am only led to assume the product was defective when purchased. My other macbooks have lived long lives of up to 5 years this is the first time I have experienced such a disappointment with regards to apple customer service.