"If a locked container alarms during screening and is not marked as containing a declared firearm, TSA will cut the lock in order to resolve the alarm."
- per the manager - mine was marked as containing a declared firearm, therefore the TSA should not have cut the lock to resolve anything.
I'm pretty sure this is where TSA generates it's "leeway" as even she isn't interpreting the rule correctly.
THE ONLY THING THE TSA CANNOT CUT THE LOCK OFF OF IS THE ACTUAL HARD-SIDE CASE CONTAINING YOUR FIREARM. They most certainly can and will cut a regular lock off your soft-sided luggage to get inside of it regardless of the fact that there's an additional locked hard-side case inside with a firearm in it. That's why you should use TSA locks on your soft-side.
OR... you can just get ONE BIG PELICAN CASE and put your gun next to your undies and travel with all of your clothes/stuff/guns inside ONE BIG LOCKED HARDSIDE CASE if you've got a big issue with the TSA going through your stuff.
From firsthand knowledge, it's a no-brainer to tell if a firearm is unloaded via a modern scanner, so that rule is crap, but as for the "marking"...
Neither you, nor the TSA, nor the Airlines may mark a bag/box/case from the outside to demonstrate there's a firearm inside. I'm pretty sure this is FEDERAL law. This isn't the same as them sticking a large red label INSIDE your checked luggage next to (on top of your socks) the locked case that has your gun in it.
So from what you've said, the only rule violated was them actually opening your medicine. I'm going to assume it's specific TSA policy for employees NOT to open anything resembling "medicine" due to liability (spilling a Centrum Silver bottle full of crack rocks all over the screening room, etc) and the follow-on inability to bring a case against somebody who may be smuggling, etc... after the evidence has been tampered with by some $10hr "screener"... but I could be wrong.
If you haven't seen this video, it's a must for flying with firearms:
Here's the website: