On our recent flight from Detroit to Orlando, on the way down suitcases were not searched. On the way home, 1 of 4 was searched, with a note from the Transportation Authority inside. Friends traveling with us had 3 of 4 suitcases searched on the way to Florida.
In January I locked my suitcase with a key lock, and the entire zipper tag was cut at the base, not simply the lock, making the bag now completely unlockable.
We use plastic wire ties to "lock" the bags - we thread them through the zipper tags, loosely. The TSA used white ties to resecure the searched cases, and as I said, a note is now placed inside.
And, by the way, the only thing in the suitcase that was searched was snorkel fins, masks, tubes, and all our shoes (water, dress, sandals, etc). Interesting that that suitcase was opened....I have no idea why.