Apple's general position on the subject of broken glass screens is that Glass that has survived the rough shipment from the factories in the Far East and been deployed by the User does not crack spontaneously.
The clearance between the screen and the top-plate (where the keyboard sits) is very small, and the hinge arrangement means that the force applied to the glass if an object is left on the top plate is very large. Something the size of a staple left in a piece of paper can crack the lower bezel or the screen itself.
Every owner they talked to recently with a broken screen has said, "It cracked by itself!" -- including the owners of Macs presented with obvious dents from being dropped down the stairs.
They will be more than a little bit skeptical. But you should present your Mac for inspection and tell your story. Your results may vary.
