In Missouri it isn't reason enough to get a warrant
A refusal of unreasonable search and seizure is not probable cause in ANY way, shape or form. We do NOT (or rather should not) have to defend ourselves against warrantless search, questioning, etc. That right is already granted to us.
However in 43 (I think its 43) states, a refusal could possibly be enough for "reasonable suspicion" which is enough for a search of your car and person without a warrant. There aren't many probable cause states anymore which require actual probable cause for search and seizure just like with getting a warrant.
Now the problem is that in certain areas of the country *cough cough* California *cough cough* it is perfectly reasonable to assume that someone with a vaping apparatus isn't vaping e-juice and it gives them reason enough there to check you out. This is one of the reason why I actually think we should start actively supporting non-smokers getting into the vaping culture (albeit at no-nicotine), to grow our base so we have more people to argue what we feel our rights are.