PAXboy: If they did not reseal or leave a note, how do you know it was TSA? ... BUT how do you carry a good pair of cutters or knife to cut them with, if you have to put all such items inside the bag?
You're right, I don't know for sure. But the TSA have plenty of reported form for failing to reseal bags or to leave a
billet doux, and I doubt that a rampie would go to the trouble of cutting off a tightly pulled cable tie just to have a rummage - one of the great things about even a cheap padlock is that it tends to persuade a dishonest rampie to move on to easier meat.
The real answer to the cutting problem is to put a cutter or knife in an unsealed outside pocket of the suitcase, if you have one. But fortunately, almost all of my ex-US journeys take me straight back home so I don't need to worry about it.