I would ask him for a printed letter from the Hermes store he went to and then you will refund him. I would say chances are he made up the story.
2. Hermes does not authenticate items, they just dont. The only way youll get them to tell you its real or fake is if you take it to the store to get repaired. They wont repair fake items. You can ask them to clean/restitch the tie and once you have it back with the letter/receipt, youre good. But if its in his hands, its probably too late for that.
Try a SCO if you refund and get back, less hassle.
+1 - It used to be that you could send items directly to their repair center, but I believe their policy is now that the items has to be sent to the repair center via a store. Generally speaking, if it has the loop, from everything I have ever read it is authentic.