If they said problem is OS simple reflash of rootfs should do (assuming your data is in /opt and ~/MyDocs). If this doesn't restore touchscreen functionality then you were lied to and it is HW issue. If you maybe installed sshd you should be able to access your phone remotely if it autoconnects to your home wlan, touchscreen issue shouldn't interfere with that. It might be possible to get rootfs img from someone with BackupMenu so set up that after flashing you can access your phone by BM (no touchscreen needed for that) and then use USB to DL all data, not sure how likely this is though