Or get tell them he doesn't have the degree certificate due to a house fire.
Tell HR he's been in touch with the University and cannot get another copy until the New Year.
That'll give him some time to look for a new job.
Or,
Do the above, find someone you trust to move into the area of the university, give their landline number to HR and get them to call and confirm attendance at University.
Each time the landline number rings they answer with, "good morning XXXXXXXXX University Records Department how may I help?"
Or
Set up an answer machine with "You have reached XXXXXXXXX University Records Department please leave a message after the tone......."
Then get someone to call back with confirmation.