Mmmm....the rest of the people have had different experiences in Vegas than me. I don't find the ventilation systems to be adequate at all. My clothes and items always reek of smoke just from walking around the casino and other places. I have to go to Vegas at least 2-3 times each year and I have to have everything dry cleaned when I come back home.
I do agree that some incidental smoke smell will probably go away within a few days, but don't take the bag if you don't want to take that risk.