Charged $900 for smoking… I’ve never smoked [USA]

Please help! I’ve never smoked in my life, but a host charged me $900 for smoking during my stay. They have a Wynd smoke detector and word from the cleaning crew that the house smelled of smoke. Airbnb sided with the host obviously because they have a ton of proof, even if it’s wrong. Does anyone know how to fight this? How do I even prove the absence of me smoking?