In this case, I would really consider reaching out to the boss and telling them what occurred & send the photo evidence. Be calm and professional and request what is due if you feel it’s worth it. This is not a good reflection of that company. As a boss, I would be very embarrassed and eager to make it right. If the boss says no then you can decide to escalate to Air (they may offer to pay 25-50% with the proof; I’ve gotten 100% before but it was some work).
That being said…
I had the same thing happen on my very first booking. What I did: (1) said nothing at first, called AirBnB. They were 0 help with guidance (didn’t know about this forum ). (2) I calmly messaged the guest that they owed me for the additional persons (evidenced on camera) & mess they left and sent a payment request. Guest went ballistic and rightly so. Why? What I requested was way too high (priced that way in house rules to detour the behavior but now that it happened it didn’t read right to enforce it so steeply). Guest refused to pay. (3) I escalated. Air got involved, billed guest for 1 extra person (because my base price would have covered the others, he just needed to be honest) and $70 for leaving vomit on my porch area. (4) I reviewed guest honestly at Air’s urging. (5) Guest gave me my first review ever. 4.0. (5) still, many bookings followed so on the lying guest.
2 YEARS LATER…take all this great advice from the hosts above! (1) Know your market and “you do you”. I ended up moving to pricing to my max capacity and it lead to hosting larger groups but also making more $$$ and reducing the sneaking (2) Decide what battles to fight. I never let stealing go (yes, I consider it stealing when you bring people you didn’t pay for) & I’ve had some guests kindly fess up and pay up while others balked. Establishing a great rapport before and just after they arrive helps (can be done via messaging; I don’t meet my guests either). (3) AirBnB will pay sometimes (they’ve paid me the 2 times I was cheated & guest would not pay but I had to fight for it; only worth it to my sense of justice but that is enough for me ) (4) I recently started only leaving enough of all supplies for the number of people booked. It’s awesome…cuts down on laundry/cost while sending a “message” (5) In the message with the access info I reiterate the number of people expected and tell them to contact me ASAP for changes. At the bottom of the message, it contains a big warning about extra people or pets.
So far I’m happy. Also, with the price increase to accommodate my max occupancy, I’ve weeded out a lot of trouble frankly. I wanted smaller groups and to be “affordable” but all it got me was issues, and now, I still get the smaller groups AND the larger groups w/o getting as many trouble makers.
PS> Whatever you decide your max. occupancy is or how you will price, be sure not to picture more of the house or set the house to accommodate more than your decided max. I offer six dinner chairs, seating for 6 in the living room, 6 patio chairs, etc. and I include that in pic descriptions ("seating for 6 at the dining table, the living room comfortably seats 6, etc.). I can sleep 10 but I’m not advertising that & I’m not looking for that kind of group.