Here is the verbose output, cut to meet the 9500 character limit. Any ideas on a fix?
avrdude: Version 5.11, compiled on Sep 2 2011 at 18:52:52
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
Copyright (c) 2007-2009 Joerg Wunsch
System wide configuration file is "/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/etc/avrdude.conf"
User configuration file is "/Users/aurelius/.avrduderc"
User configuration file does not exist or is not a regular file, skipping
Using Port : /dev/tty.usbmodemfd16311
Using Programmer : arduino
Overriding Baud Rate : 115200
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: ser_recv(): programmer is not responding
avrdude: stk500_recv(): programmer is not responding
avrdude done. Thank you.
Hmmm. Not really sure how to do that. Pressing reset on the board flashes the LED at L. If I try and upload any sketch, it hangs and the LED stays on. Not sure if that is helpful
If that doesn't work, you can use an "ISP" programmer (another Arduino compatible board will work) to try to restore the processor. This should get you started... https://www.google.com/search?q=arduino+atmega16u2+isp
I have not done it myself so that will very likely be the only guidance I can provide.
I uploaded the ArduinoISP sketch to a Mega2560, connected the appropriate pins (10-13, 5v,gnd) to the ICSP header on the Uno. Attempting to burn a bootloader with the board set to the Mega and Programmer with Arduino as ISP returns the same error. The yellow "L" LED stays lit on the uno until I reset it.
And I feel like an Idiot. I was using the wrong sketch to upload. I need the Standalone AVR ISP programmer sketch from Adafruit, not the ArduinoISP sketch in the example folder. All seems to be well. Thanks everybody for trying to help me out.