Possible Clues:

• Nabber's cry
• "You fell for it!"
• 'You fell for it!'
• 'Aha!'
• Prankster's cry
• You're caught — I understand you
• ''I fooled you!''
• Informal ''I understand''
• Stagecoach rickety, case craftily purloined -- you've been had!
• Subtitle of this puzzle, perhaps