@Dain30 It's not clear to me from this description what rule or policy was broken. What happened that resulted in the police going to your house? Did the number of people exceed the guest count in the booking - and if so, do your House Rules explicitly prohibit unregistered guests? What measures do you have in place to monitor the property and prevent situations where you lose control over it?
There may indeed be people using illegal drugs in your home, but if the police uncovered no evidence of illegal activity, you don't have much to go on. It's not a crime to look "sketchy" in someone's potentially biased opinion, and it's plausible that your guests were under the influence of substances that aren't even illegal.
You might try coming up with a pretext to enter the property, making sure to give appropriate notice via Airbnb messenger, and inspect it for any signs of damage or wrongdoing. If you find anything that merits evicting the guests, you'll need a stronger case than the police seemed to offer you.