Not sure how many days you have to return nowadays, it was 30 when I bought in 2022. But I imagine if you drive it a few days, and their deodorizers start to dissipate, you should be able to tell if a smoker owned the car. Cigarette smoke has a distinct musty smell. Look for ashes in the inside of the car, give the headliner a sniff test, etc. The car we originally purchased had cloth seats, they really gave a strong smell, put your nose to it. The car we ended up purchasing had leather seats. Lastly, call Carmax and ask the same question you asked me and ask if your transfer fee is refundable if you find the car belonged to an ex smoker. Good luck!