Hi Karin
Sorry this happened to you. However, as a long established host, it really pays to be familiar with how BNB works.
Knowing how to raise a concern with BNB and having their phone number I find are two essentials to being a host.
You could have contacted them by going into the booking reservation and flagging it with them (if you go into a booking confirmation you will see there is a section for you to do this) . Alternatively you could have called them or used social media.
All the ways of contacting BNB are outlined in the 2nd post in Community Help - you can also use Google to find the number.