your friend's bag was inspected by the TSA (Transportation Security Administration.) while bag checks are as old as flying, it is new that they feel compelled to notify you. the letter looks like this:
![](http://backdrifts.net/files/images/random/tsa_inspect_card.jpg)
they also secured a plastic tie to the outside, to show that the bag had been inspected. It happens to me all the time. Of course, that's because I usually use National Airport, and I usually pay cash.
on edit, I notice that this was internal EU only, which rules out TSA,Did your friend, by any chance, fly out of Rome? Where the letter code for Ciampano International Airport just happens to be...CIA?