Last week's exercise, intended to teach 300 children ages 11 to 15 how to read maps, has outraged residents and officials in Amersham, Buckinghamshire, The Daily Telegraph reports.
Older Explorer Scouts portrayed Prince William and Middleton as children playing terrorists abducted the girl.
The Prince William character rallied the Scouts to find her, and teams hunted for clues over 12 miles.
Ros Aitken, a town councilor, said, "I'm horrified that something like this has taken place."
But organizer Brian Shelley said, "I do not think it was inappropriate. The Scouts loved it and found it very amusing. Nobody raised any concerns on the day, so I'm surprised to hear if there were any."
He said it was a way of marking the royal wedding.
Security has been heightened around Middleton since the engagement was announced.