Depends on the airline. If someone forgot to show up with your airman certificate or medical or a Fed loses one of your certificates, you just call scheduling - they activate the opspec exemption that allows company pilots to operate without their permanent certificate, and they generate a company temporary certificate (basically saying the company has a copy of your airman's certificates on file), you go to your email/hi6, print it out and carry it until you get a permanent replacement. Once you get the permanent, you stop by the chief pilots office and the chief pilot verifies you've got your permanent certificate and they cancel the company generated temporary one. The caveat is you can't fly international with the company temporary certificate.