Hey,
I may have a solution to this problem, it just worked for me. I have a thunderbolt which hadn't been dropped or abused but somehow parts of the screen stopped registering. I couldn't type well or use it for much and was offered a referb again but declined because i've had more than one issue with this phone. Anyways, after being told that I could get my date moved I got a new phone but wanted to see if i could fix this one. I watched this youtube video and got the idea that it might just need the 3 ribbon cables between the screen and motherboard reseated. I took it apart to right before the complex part that you need to unglue anything and put it back together. Problem solved.
I find this unfortunate that they don't keep techs in the store to perform this kind of easy fix...
Still getting something else (htc rezound) but now i have an extra or can sell this for some of the price difference in the upgrade.