I have had this issue before with an LCD screen where pressure had been applied on the screen during transport, i.e. screen leaning against a seat arm rest.
Would there have been anything pushing in front or behind the screen at any stage?
A few examples to give an idea:
[li]A child or someone else accidentally poked the screen while pointing something out.
[/li][li]A heavy object was placed on the screen lid while down.
[/li][li]An attempt to close the screen while something was on the keyboard.
[/li][li]A solid item placed above the screen in the laptop bag. E.g. power plug, mouse, etc.