There have been many threads started on this issue. It appears to be related to something that occurs during Windows Update. Not sure if it's firmware or driver related. Nevertheless, some of us have had success getting our touchscreens back by performing the "battery kill" sequence. It goes something like this:
- Run the battery completely bone-dry dead
- Leave the unit sitting dead on a table for - literally - a couple of days (cool down time?)
- REMOVE the external keypad
- Plug in the charger and allow the Surface to charge and/or start up on its own.
I hope this helps you. I know it has worked for me several times...
One other trick that worked for me (albeit surprisingly) was checking for updates (using the keypad, as the touch screen was dead...) and running the updates WITHOUT the keypad attached. Somehow, after the update and re-start, my screen came back to life! (???!!)
So, there's something strange going on with Windows Update on the Surface 2.
Best of luck to you!!