Black Display -> what happend?

[Boy2006]

Hey
Last week i was sitting in the Train and the Display get black from outside to the inside and my Thinkpad still run.
So today my dad (i dont get the power to check it ) get a look and the try a little around (he is also an it engineer) and the found it was FN + F7.
How could that be? I believe i never push it when i sitt in the Train.