/dev/ttyACM0 disappeared (previously working)

Hi all! I have a very strange problem: My Arduino Uno rev3 was working just fine for months and some minutes earlier /dev/ttyACM0 disappeared (I’m running on a Linux PC). I unplugged the USB cable and plugged it back, but nothing! I tried:

ls /dev | grep tty | wc

and there’s no device appearing when I unplug the USB cable from the board and I plug it back. Is it dead? Any ideas?

I also restarted the computer… nothing!

Note: There is some program on the chip and it’s running fine.

=( I think I burnt it... for sure it's the AVR328P that it's burnt, but it might also be the on-board Mega16U one as well... While trying to re-burn the bootloader using an FTDI breakout I got:

avrdude: AVR device not responding
avrdude: initialization failed, rc=-1
         Double check connections and try again, or use -F to override
         this check.

Rest in peace my dear Uno!