That’s right. They wouldn’t need the pharmacy data—they’d only have to look at your Obamacare records and know what you were prescribed. Then it would be up to you to prove you didn’t take it.
Where does state vs. federal control of 2nd Amendment rights figure into this? In my state, it is fairly difficult to lose gun rights — basically only if you are a felon or involuntarily committed (and a few other things like certain domestic violence). This article seems to imply the feds can supersede the state. You could be perfectly clean with the state yet the feds grab your guns.