Shoppers were horrified to see a sticker on a book about Madeleine McCann which read, "when it's gone it's gone".
The label advertised a 60 per cent reduction on a new study of Madeleine's disappearance in discount store The Works, where it was spotted by a Twitter user, according to Daily Mail.
She posted an image of the blunder with the caption, "Of all the price sticker choices..."
Replying to the tweet, one user wrote: "Shame on you @TheWorksStores."
Another person hit out at people who were making light of the mistake, with one writing: "Do people not realise this is someones child?"
The book, Madeleine McCann: Ten Years On,
develops the theory Madeleine left her bedroom in the Portuguese resort of Praia Da Luz of her own accord on the night she disappeared.
Its author, Danny Collins, claims the shutters can only be opened from the inside and the toddler wandered outside to look for her parents.
She was then kidnapped by a man who witnesses saw carrying a girl that night, the author claims.
Afterwards, he believes he child was sold on to Romany gypsies.
Madeleine disappeared 10 years ago this month, and since then numerous theories have been put forward in an attempt to explain what happened.
Detective Colin Sutton said last month a trafficking gang could have snatched her to replace a dead child or she could have been snatched by a paedophile.
But the former Scotland Yard officer theorised the "most likely and credible scenario" for Madeleine's disappearance was a targeted kidnap.
At the 10th anniversary of their daughter's disappearance, Kate and Gerry McCann said they would "never give up" hope of finding her.
Kate, 49, said: "I obviously have to think about what age she is and [choose] something that, whenever we find her, will still be appropriate.
"There's a lot of thought that goes into it. But I couldn't not... she's still our daughter, she'll always be our daughter."