I’ve never had TSA search a phone
I haven't either. I know two people that had to unlock their phones so TSA could look at them. What TSA was looking for, or if it was just random, my two friends do not know. And does that really qualify as a search? Depends on definition of a search. In the cases I knew of TSA only looked at the Home Screen. Was TSA looking to see if the phone actually was a phone or looking for something out of the ordinary?
I have personally been through a very thorough search at an airport. Oslo Norway, returning to the U.S. Supposedly randomly selected, which I don't entirely believe. I was taken to a separate room, my passport taken, and told to strip to my underwear. My clothes were searched thoroughly by hand feeling every inch of my clothing. I was not asked any questions. I was never told why even though I asked. I suspect my name, or face, matched someone of interest.
What was strange is that I was allowed to hand my carryon to my wife, which contained my phone and laptop., such items never searched. I suppose they would have searched the items if they wanted. The entire experience was enough to make me extra cautious.