The pilot was at 37,000 feet and said the object was above them. Commercial planes top out at about 42k feet and would have shown up on ADS-B. A U-2 flying at 60k would look like a long cylindrical object about the size of a cruise missile (in the same way a 747 looks small from the ground), and not show up on instrurments. Oh and they regularly fly out of Nevada to swoop down over New Mexico/Texas on their way to Mexico and Central America.
If they are really interested in privacy then they should be doing for all the applications including their own.