There is commonly a law like RCW 69.50.309 which says that
A person to whom or for whose use any controlled substance has been
prescribed, sold, or dispensed by a practitioner, and the owner of any
animal for which such controlled substance has been prescribed, sold,
or dispensed may lawfully possess it only in the container in which it
was delivered to him or her by the person selling or dispensing the
A controlled substance is "a drug, substance, or immediate precursor included in Schedules I through V as set forth in federal or state laws, or federal or commission rules". Schedule V includes some opiates with low potential for abuse and dependency. It does not include prescription antibiotics, and does not include Ibuprofen and other OTC NSAIDs. The cop may be right about keeping your narcotics in the original container, but wrong about anything less. I can't presently locate the Oklahoma analog of this law. After diligent searching, I even suspect that Oklahoma does not have such an "original container" law. It would count as a "counterfeit substance" if it is a controlled substance and is in a container with labeling that is not that of the original distributor, but if the contain is completely blank, it is not legally a "counterfeit substance". And again, that only applies to controlled substances.