I don't think you're paranoid at all! You're being practical, logical, and responsible.
I know there's so much controversy over flushing medications. I can understand why, and I understand the potential dangers it possesses.
Some drugs, like the patches, I see no other way. And I'd make sure they're flushed and don't sort of pop back up through the pipes!
Knowing the controversy, even my most recent hospital stays and doctor visits, they have all still advised me to flush the meds, -- telling me verbally and it's on written instructions.
I don't know if it's "safer" to flush if you have a public sewer system as opposed to a private septic tank? I really don't know. But as recently as a few months ago, the hospital where I had my last hip surgery done instructed me to flush 'em.
They're not making this disposal job easier, are they?
I'd contact the Police or Sheriff's Dept or even your local pharmacy. Perhaps different towns, pharmacies, or offices do "collections" on different days or times of year.
I get nervous about handing over prescriptions of active medications to other people,....Maybe I'm paranoid.
Flushing is the only way "I" know the meds are gone for good and not getting 'accidentally' into other hands.
But the doggy poo bag is a GREAT idea! (Or a baby diaper!)