I think they do this more with credit cards where you can chargeback than debit cards which are more like cash, unless fraud is alleged.
The smartest thing for next time is use a travel agent and then this never arises. For this time photocopy your debit card and maybe ID card on the bottom of a sheet of paper, and on the top, print a short letter you purchased the ticket for Mr. A and paid with the below debit card and nothing else. Ask Mr. A to keep possession and shred or burn it afterwards. Otherwise go to the airport with him.
Note, yes it could be Ms. A Mrs. A and her not him.