I never managed to contact a human about it.

The airbnb dispute process allows you to request money from the host, but doesn't let you get a full refund - only ~80%. In my view, the house not existing warrants at a minimum a full refund.

Instead I took it to my credit card company and got a full refund from them.

The money is released to the home owner 24h after the arrival date if no complaint has been raised by the renter. Luckily haven't had a reason to test this though.