How do you fix a touch screen that no longer works?

A Nisbets sorry to hear about your phone. First off “I did the rice thing and then left it in the sun for a few minutes “ does not do anything. It is the equivalent of doing nothing, So all you are doing is wasting good rice.

The very first thing you want to do is to not try to restart/sync the phone. This may further damage your phone. The next thing to do is to clean it. Disassemble your phone using these guides. You must remove all the EMI shields of the logic board. If you do not remove those you are not cleaning 3/4 of the board. Clean everything with +90% (no less than 90%) isopropyl alcohol. Follow this guide, and even so it was written for Apple iPhone 3G all the points are still pertinent to your phone. Pay particular attention to the SMD components, check for charred missing or broken missing. You can then dry the board in an oven or equivalent at 220deg F (not higher;-) for a few hours. Best way to clean it would of course be through an ultrasonic cleaner. Consider professional help with that When it is properly cleaned, replace the battery. All these steps are to avoid delayed failure caused by corrosion. Once all this is done, reassemble your phone and reevaluate. It is possible that it is "only" the digitizer that may have failed vs. circuit board damage. In that sae a new display assembly replacement should fix your phone. You can only determine what is going with your phone once you cleaned the phone properly.