Lantern of Insight doesn't change anything about how
Sleight of Hand works–NAP is not entitled to know which of the two cards AP puts into their hand, regardless of whether or not the top card of the library happens to be revealed at the time.
In paper play, the NAP may be able to figure out which card was picked by tracking the physical motion of the cards as AP performs the actions Sleight of Hand calls for, but that's on them to pick up on–it's not information the game provides.