The bear which has a read bow tie and a heart on its foot, had been bought by Oliver for Valentines’ Day, which fell a week after she was brutally murdered by her boyfriend.
Rosie’s family say they feel “gutted” by the disappearance, and appealed for the bear to be returned.
CCTV footage has been released by a resident of Village Drive, Ribbleton, of a dark-haired woman wearing a rucksack, crossing the road to look at the memorial garden, then placing the bear in the bag and walking away.
Alice Hodgson, Rosie’s sister, said: “Oliver wanted to get his mum something for Valentines’ Day, so he got the bear and it was put with all the flowers left in tribute to her.
“It was out for a while, then we picked it up and cleaned it. When the memorial garden and bench were finished, we put it on there.
“It went missing the same day. We’re gutted. It’s a teddy bear, but more than that, it’s what Oliver wanted for his mum.
“I don’t like to think it’s been taken maliciously, but it’s in a memorial garden, it’s quite clear.
“I hope that if someone sees the appeal for the bear then it will be returned, it can be cleaned, and we can put it back out. I hope the appeal pricks someone’s conscience.”
The memorial garden was finished on October 5 at the junction of Village Drive and Pope Lane, close to Rosie’s family home, and where flowers were left in the wake of her murder in the early hours of February 7.
>>>Read about Rosie's story by clicking hereLand was donated by Ribble Village Surgery and work to install a bench, shelter, trellises and landscaping was carried out by friends and family. Money was raised by the local community and donations of materials were given by local companies.