Sorry, but "it was not the TSA" just because they didn't put in the piece of paper??? That's not proof of anything. The TSA doesn't believe they have to "play by the rules" and if they made a mess of your luggage then they would most likely NOT want to admit it! T
My bet based on the description is on the TSA. Thiefs just steal they don't mess around. The TSA messes around. If a Delta person had been doing it they probably just would have grabbed the "sealed containers" to open later and see if they were valuable. (Or course it's possible the TSA was checking to pass the info onto someone else to take the valuables.. see LAX)
(Does anyone else remember the poster a while back who didn't have the "piece of paper", but had a TSA agents shirt LOL!)