Default Unfriendly screen

Hi guys,
a strange thing happened to me - I accidentaly slept with my head right on my galaxy S3 and when I woke up, I wasn't able to use my phone, because the touchscreen was not responding. Power, volume, home, back and menu buttons are working, however I cannot select or do anything on the screen. I did a factory reset, took out the battery, waited for some time and etc. Nothing helped though.
What could have gone wrong?

Have a nice day