Factory unlocked 4s kaput after ios6 upgrade

Started upgrade to 6.1.2. Phone froze with progress bar over an hour. Restarted (yeah, I know). Got Apple screen. Forced restart, only got apple screen. Followed instructions in all support articles. If I continuously held power + home, apple logo disappeared, reappeared, then screen went black (feels like firmware problem or like the old days of PRAM zapping). With black scren, plugged into USB. iTunes icon (plug in screen) appeared. ITunes does not recognize phone. Restarted computer. OSX (10.8.2) and iTunes (11.0.2) up to date. Tried all permutations of restarting and replugging. Did forced resart of phone while plugged in and still cannot get past plug-in screen.

Help! I feel like I'm stuck in an Escher paiting!