@Steve2924
Yes, it's always a tough situation when this happens. I wish they wouldn't do this. I really hate having to deal with this.
My approach depends on whether they're deliberately trying to hide it or not.
If not, I'll approach them and (nicely) tell them they either need to leave, or pay up, per the terms of their booking. For me, this is the best way, usually fair & mutually agreed, and helps avoid retaliatory reviews.
But if they're obviously deliberately trying to hide it (and I really hate this), considering that Airbnb is unlikely to help, but more likely cause trouble for >you<, I usually just let them believe they're getting away with it.
If there's no serious damage at checkout, then I'm really nice, I let them go, and let them write a glowing review of their stay.
If you call them out or make a claim, the likelihood of a retaliatory review is very high, and it's unlikely Airbnb will help, and may actually cause you significant pain. And this stuff sticks with you for a long time.
You of course, should tell the absolute truth in your review of the guest. This is really the only recourse you have without risking pain of your own. And if they didn't cause damage, just let it go. Your review of the guest will likely be pretty painful for them for future bookings.
I'm sure others will disagree with my view, but this isn't my first rodeo. I've been thrown from the bull a few times. And no, its not fair. Yet avoiding both injury and insult is probably the wisest course, since the other choice is pretty risky and likely to hurt.
Sorry.. It's just the nature of the beast. Good luck.