I just recently had a guest that scammed me as well. Stayed for 5 days out of a 7 day stay and then contacted Airbnb and obtained a complete refund without my consent based on fabrications.
I suspect both my guest and your guest has done this before.
To make matters worse, my listing was deactivated for 5 days based on this lie.
However, after 5 days and numerous phone calls and emails, my listing was reactivated.
Now almost two weeks later, this issue has been resolved thank goodness. I am very grateful to the customer service representative that i have now that fixed this issue.
Keep calling and keep emailing.
I figured out that many CS reps (outside of the US) have issues with determining if a guest is being deceitful, and they tend to look over glaringly obvious signs.
Good luck and I’m sure you will eventually find a CS rep that can handle your case fairly.