Can you get charged? technically while you should not be if that is the only fact as simple possession of the item does not show it was consumed, with that said that kind of thing happens (charges without real probable cause) all the time, for a misdemoner DUI all that need to happen for you to be charged is a prosecutor signing a piece of paper. Could you be convicted is a different matter. If there was bad driving, you did badly on Feid sobriety tests and and or admitted you had used a substance you definitely would be charged.
Had you smoked said drug? Did you take any field sobriety tests? Why were you pulled over? Was there any alcohol or any drug or metabolites in your system? Did you admit to any drug use or drinking? way to many questions that would need to be asnwered before knowing a conviction would be likley.