The smoke smell was gone before the smoking guest and I didn't need to borrow the ozone machine after all. Just as well, because I don't think the owner found it. The current occupants of that room are a lovely Italian couple. They're also smokers, although they say they would never consider smoking indoors at a B&B. The good thing is that if any odor had lingered they wouldn't notice it. Anyway, I'm breathing a big sigh of relief.
By the way, fabric freshener spray rocks!