@Mallory89 ,
Sorry to hear about this, unfortunately I have heard the same thing from other hosts who have reported a party. Some would recommend you to consider putting your listing on another platform because it could take weeks to get this investigation cleared (based on other similar cases - I hope not but that is what it appears to be).
Our recommendation is the following:
1) Message the guests on the Airbnb platform (to show a paper trail) about the violation of no party rules and no unauthorized guests. Ask them to immediately remedy this or you will contact the police to break up the party if there is no resolution immediately. You will state I can monitor this via the safety cameras on the outside. I would also call the guests as well and reiterate what your wrote them on the Airbnb platform and refer them to the terms and conditions of their rental and the number of guests allowed. Many insurance companies will not cover a stay if all the guests are not listed on the reservation. I have seen situations where the guest’s guest who was only listed as a guest with no name, cause damage and Airbnb would not cover it even though the agreement with the guest who made the reservation stated they are responsible for the unit while they stayed there. We need all names of all guests or we do not allow to them on the premises or it voids out coverage for your short term rental.
2) If they ignore or do not respond, call the police and explain that there is an unauthorized party on your premises and have them break it up, especially if there is illegal drugs. If you know there are illegal drugs present and do nothing you could potentially lose rights to your property depending on what state and jurisdiction you are under. I had a friend who was in a process of divorce and her ex was staying at the home they were both listed as owners and he was allowing other guests to use illicit drugs. She was told by a lawyer if anything happened she would be on the hook as she is still legally an owner even if she was not present and no longer lived there.
3) I would write in their review at the end of the 14 day period, that you do not recommend them because they do not follow house rules. If they write a bad review of you with false claims, I would ask Airbnb to review the messaging between you and the guest and remove their review due to a retaliatory nature.
Let us know what happens…