If you're president and you've done something morally abhorrent and politically unpopular, like setting up a "zero tolerance" policy at the border that tears children from their parents' arms, there are a few ways you can handle the fallout. You can reverse the policy and admit it was a mistake. You can make a case that it was justified.
Or you can claim that despite widespread comments about that policy by you and your aides, and literally thousands of news reports documenting what went on, none of it actually happened.
In an absolutely gobsmacking new interview with Jose Diaz-Balart of Telemundo, Trump attempted this up-is-downism with regard to his administration's family separation policy, in which thousands of children were taken from their families at the border.