16U2 firmware

Hi, I seem to have bricked my Arduino (Uno R3) because it lost it's USB controller drivers, both the 328p and the 16u2 can be controlled with an avrisp mkii, but i can't comunicate with the Arduino, because the PC won't recognize the Arduino, but power is on when connected over USB. So the problem seems to be the 16u2. As I found out I have to write the Firmware to its flash, but i can't find it anywhere. (I'm using Atmel Studio to communicate with the chip) Is there a possiblity rescue the chip?

Did you look in the /arduino-1.0.5/hardware/arduino/firmwares/atmegaxxu2 folder?

I have tryed the file “Arduino-COMBINED-dfu-usbserial-atmega16u2-Uno-Rev3.hex”, but then Windows recognizes a “Atmega16U2”, but there is no com-port in the device manager.
But why is the original file not working as expected?

Edit: Ok this was the wrong file, it worked for me with the “UNO-dfu_and_usbserial_combined.hex”!
Thanks a lot!

Don't know. I use FTDI chip in my designs, no 2nd set of firmware to fool around with until I tackle IO that needs it.