I have ever seen this happen spontaneously was when I was once advising some clients on data processing for an oceanographic survey. It was a freezing winter's day, and we had been out on a boat for several hours. One of the clients had brought his laptop along, but didn't use it.
When we came ashore we went straight into a pub to get warmed up (inside and out), and this client got out his laptop and fired it up. Within a couple of minutes of being turned on there was a sharp cracking noise, and the screen had several cracks radiating from one corner.
What had happened was that the LCD screen (which has liquid inside) had frozen, and hadn't had time to thaw out before the warmth of the display lamps hit it.
Other than that one incident I have never heard of a screen cracking itself, and I don't hold out much hope for your claim to be honest.