Hi,
What you see with the 'ifconfig -a' is what the kernel has recognized, even those that are down. If the output does not have a device you expect then that is when you have to start reasoning as to why or what is happening.
I would look at the output of the logs. Start at 'dmesg' to see if the device is listed or sometimes a device can be in the output but not properly identified. That is where you start to trail things. Sometimes it is lack of having 'firmware' in place or even incorrect modules/drivers. You as the admin must learn to diagnose and identify errant things. Then start looking for a solution.
At first I thought it could be udev problem but now it may just be a hardware failure. Do you have another NIC that could be tested on this system?