Default [Q] E300K - Baseband: Unknown; IMEI: Unknown

Flashed a rom that included a different modem. Now bad EFS. Stupid me thought CWM would back-up EFS, it doesn't. Am I finished?

I don't understand how flashing rom/modem can corrupt EFS... (And then not stock rom fixing it if it does). How does it become permanently broken one way?

I might be able to make an EFS copy off a friend's S4 but wouldn't that duplicate our IMEI numbers? I don't think that is good... if installing custom rom/modem can corrupt it then surely there should be a way to just hex edit the numbers or something.