Cops should have called animal control for the mutt. Leaving it there creates a traffic hazard AND is irresponsible handling of a citizen's private property.
Prescription drugs are supposed to be kept in their original container. If they aren’t then the cops suspect you are trying to traffic them to others.
There are still many facts missing from this story though.
He might have been on several meds and used one of those "daily pill" cases to carry them.
If the passenger was doing this then yes, they could have arrested him. Not because he was carrying something that he was not prescribed but because he was not carrying it in the "correct" container.
if they belong to the passenger there’s no law broken.
It's Texas. My cousin was driving two months after a massive surgery with her two children. (Ages two and seven) She was pulled over for a traffic violation. She had a prescription vicodin in her purse (which she had a prescription for) just in case she needed it. They searched, found the pill and arrested her on the spot. We were all scrambling to get the kids and she spent the night in jail.
Texas is terrible about the War on Drugs. Remember, this is the state where the women were strip searched on the side of the highway. After traffic infractions (that's where they get a ton of money) their main concern is drugs. Protecting and serving? Not so much.