Kanatapilot - in your post you said that

"VISA's evidence was that Air Canada provided a blurry copy of a credit card receipt with barely readable inprint and signature. No charge date was legible."

Does the signature match your father's? If it does not, have your father call Visa and ask that a fraud invstigation be started. He can state that he did not authorize this charge and the slip does not have his signature.

If this does not work, I would suggest that your father go to the local branch of the credit card issuer and ask for a number to call to get help. With CIBC it is Customer Care - and they will follow up and respond with in a couple of days.

Hopefully this will helps and good luck.