How to restore IMEI and get back network functionality? Related, but no solution: How to restore my IMEI on Galaxy S if I don&#39;t have a backup of /efs?

My IMEI has turned blank after a nightly update, I can see it is blank when typing *#06# and I have no GSM functionality. Also baseband version is unknown.

I do have a backup of the /efs directory. I have restored the contents. But even before restoring, I checked the md5sum of the mps_code.dat file, and it was the same as the backup, so I didn't have my hopes up.

Nevertheless, I did a full overwrite of the contents with my backup. Rebooted, no change.

I have also tried to do a factory reset, reinstall Cyanogenmod, two different versions, wiped cache, Dalvik. Remove the battery, SIM card, USB cable.

I am willing to install the stock firmware, if I could find it, or patch the modem firmware somehow. Where should I go from here in a situation such as this one?
If you also have "No Baseband" in the about screen, You can try to flash only the modem and see if it help.

e.g With Samsung devices, I usually use Odin with the ROM from SamMobile, 
I extract the modem file from the archive and put into a new .tar file, and then flash the new file with Odin.

On Linux i can use Heimdall which allow my to directly flash a specific region like the modem.