Have I completely lost my IMEI?
Your handset is not damaged, not totally.

But you do need to get some professional help, someone who is willing to carry out the procedure in restoring it, provided that someone has the necessary tools at their disposal.

However, you can fix your IMEI using a highly specialized but expensive repair box such as Z3X, NSPro, to name but a few.

Mostly, smartphone users do not have access to them and only repair labs or specialists have them.