Here's the link and some info from Scopes:
http://www.snopes.com/horrors/parental/kidnap.htm
Claim: Children are spirited away from amusement parks and shopping centers by kidnappers who alter the appearance of their victims before smuggling them out the exits.
Status: False.
This type of tale that has been circulating for decades, always involving the kidnapping of children from family-type public places such as amusement parks and shopping centers. A kidnapper snatches a child away from an inattentive parent, drugs it, and hustles it into a restroom; there the abductor performs a quick haircut, dye job, and clothing change on the child to conceal its identity (and sometimes to obscure its gender) and wraps it in blankets before attemping to quickly and quietly spirit the child off the premises. Meanwhile, a vigilant security force has sealed off all the exits, and the attempted kidnapping is thwarted either because the kidnapper realizes he cannot escape undetected and simply abandons his intended victim in the bathroom, or because the child's parent is monitoring the exits (in person or via security cameras) and recognizes the child by its distinctive shoes, which the kidnapper has neglected to change or remove...
Over the years, this story has been set in virtually every type of locale where families gather with large numbers of strangers, such as shopping malls, beaches, carnivals, fairs, and amusement parks. Since the details of urban legends tend to localize on the most prominent examples of their kind, this legend has become more and more associated with places such as Disney theme parks and Wal-Mart stores, both examples of well-known large facilities frequented by families with children, and both part of huge corporate enterprises. (In truth, no child has ever been kidnapped from a Disney theme park, and although the abduction and murder of 6-year-old Adam Walsh led Wal-Mart to create their Code Adam protocol for locating missing children in their stores, Adam Walsh actually disappeared from a Sears outlet, and no evidence was found to indicate that the abductor had made an effort to alter Adam's appearance.)