The girl was in the toy department at a Savacentre store, shopping with her mother and nine-year-old brother on Christmas Eve, when she discovered to be missing.
Less than an hour later, the store, in Colliers Wood, south-west London, received a telephone call from a neighbouring resident, who said the girl had been handed to her by an unknown man.
The girl later told her mother that she had been taken from the store by a middle-aged man, dressed in black, who had told her that he was called "Uncle Christmas".
Scotland Yard said the girl had been taken to a nearby park and then released.
It was understood that she had been subjected to an indecent assault, but the Yard would not discuss what had happened to her.
The mother, who has not been named, said: "At the time my daughter was missing I thought she was probably still in the store.
"It was not until I got her back that I realised how serious it might have been.
"I'm so relieved to have her back and that she's safe, but I feel shocked when I think how much worse it could have been."Reuse content