It is possible that any certificate you got in 2006 has expired But the state where you were certified should have the records. Contact the State Licensing department and start there to see if they have a copy.
If your state required your position as a CG to have a license, they may have a copy. it but my guess is since you haven’t worked since 2006 and your certificate elapsed you may need to go through the certification process again. Do you remember the certificate number? The school where you took classes for your re-cert. They may have a copy as well Good luck!
Hopefully someone can answer this. I would have said the facility where you were trained. Unless your state or county keeps records, you are probably out of luck and may have to take the training again.
But the state where you were certified should have the records. Contact the State Licensing department and start there to see if they have a copy.
Do you remember the certificate number? The school where you took classes for your re-cert.
They may have a copy as well
Good luck!