Caitlin Barclay and her mum Lindsay spent two days getting up at 4am to decorate Sandall Park with nearly 500 coloured ribbons to raise a smile and add a splash of colour to the park during the coronavirus pandemic.
But dozens of the bows – which have been in place since April – have now been torn down.
A spokesman for the Friends of Sandall Park, the volunteer group which looks after the park, said: "Caitlin and her mam, ably assisted by driver dad, spent hours putting the beautiful bows up around the circumference of the park - at the crack of dawn. They have brought great pleasure to a great many people.
"Unfortunately, someone has seen fit to rip a full length of them down. This could have been malicious, it could have been someone who didn't know any better, but whatever the reason - Caitlin is very upset. It took her hours to make them.
"She is going to make some more to put up. If you see any that have been torn down, please make every effort to get them back on to the fence so Caitlin doesn't get to see them and isn't upset again. Thank you.”
The youngster has estimated 70 of the bows have disappeared.
The pair also tied dozens of ribbons to railings outside Doncaster Royal Infirmary at the height of the pandemic.