The Courier for the Kansas City Mob was bringing $40,000 a month back from the Tropicana. The Stardust skim was much larger and that is calculated in the millions every year. Despite the fact that Lefty Rosenthal was an informant, the Stardust courier was never intercepted. They did set the FBI up one time to intercept a courier. The problem was the sack contained cookies. The guys from the Bureau laugh about that now. I bet it was not funny that day.
Here is a clip of Carl Thomas (he worked at both the Stardust and the Tropicana during the times skimming was happening) telling Mob boss, Nick Civella about skimming.