Revealing mistake: In the scene where Jennifer Love Hewitt and Jackie Chan are on the top of the building, trying to plant the bug on the briefcase, and the men all attack, as Jackie is hanging over the edge Jennifer has a man on his knees. If you watch closely, or in slow mo, she is about two feet away from actually hitting the guy.
Revealing mistake: When Chan is trying the tuxedo for the first time, he activates de ingravid mode and then falls down from the ceiling. The falling mat is noticeable under the rug, because it's flat in further shots.
Chosen answer: Since Del knew that the tuxedo actually belonged to Clark, she most likely thought that the watch and shoes did too.