The silver and gold painted urn was taken by burglars who broke into the house on Clopton Road, in the Garrett's Green area of Birmingham, last Friday.
The urn contained the ashes of Catherine Farrell Breen’s daughter, Phoenix, who was stillborn almost 10 years ago.
Catherine lives at the house with her two children, aged seven and eight. Their Christmas present, a Nintendo Switch, was also stolen by the thieves.
Locals clubbed together to buy them a new one but they remain heartbroken and want their sister back.
The family light a candle for Phoenix every night and still celebrate her birthday each year with a cake and a balloon release.
Appealing directly to the thieves, Catherine asked for the urn to be left somewhere so it can be found and retrieved, adding that Phoenix “is ours and her urn is the grieving process”.
“The urn is not of value except for what it means to me," she said.
Det Con Rebecca Woodcock, who is leading the investigation for West Midlands Police, said: “We understand that the urn was in a box and that the thieves probably just saw the silver and gold painted details, and took it without looking carefully to see what it was, as they didn't want to spend too much time in the property.
“Catherine has been very upset and feels responsible for the loss of her daughter’s ashes and my main concern is to get her baby Phoenix returned to her, where she belongs.
“I’d appeal directly to the better nature of the people who took the urn to do the right thing. Take the urn to a safe location, or give it to someone who is able to safely return Phoenix’ ashes to Catherine and her family. They could even give an anonymous tip to Crimestoppers if that’s what it takes.”
Officers understand that there is a possibility the burglars may have discarded the urn somewhere by now.
They are urging people in Birmingham to keep a look out and get in touch with any information via Live Chat on the West Midlands Police website, quoting crime reference 20/193726/22.
To give information anonymously, call Crimestoppers on 0800 555 111.