A Maple Ridge, B.C. boy and his family have issued a plea for a thief to do the right thing and turn in the 12-year-old's prosthetic arm.

Callum Davie was born without a left forearm, and relies on a custom-made attachment to ride his bike.

On Tuesday, his bike was stolen from outside his home, and his arm piece went along with it.

"I was really sad," Callum told CTV News Friday.

"It's just taking away from him being a kid, just riding his bike," his aunt, Breanne Davie said.

The arm is red with white maple leaves, and the end screws on to an attachment on his handlebars.

Incredibly, Callum's father spotted someone with the boy's bike on the day it was stolen, the family says.

"He saw a guy riding the bike down the side of the road so he got out of his truck and confronted the guy and took the bike back, and the guy gave him a story about where he found the bike," Breanne said.

So they got the bike back, but the prosthetic was missing.

"I don't know why they even took it off because it didn't really make any difference," Callum said.

Without the prosthetic, it's not safe for Callum to ride his bike.

"The artificial limb… that has been taken away decreases his ability to live an active life," explained Rob Larman, director of the War Amps' Drivesafe program. 

"They're so customized you can't just go to a shelf and pull it off, you know, there's a huge process."

A Vancouver-based company has offered to cover the cost of replacing it, but making it will take time.

Though funds aren't an issue, the family says many have reached out, offering to help. They're encouraging people to consider donating to the War Amps. 

Meanwhile, they just want the arm back so Callum can get back to doing what many take for granted.

"It would just be awesome if that arm just turned up. I mean, it's kind of a little like a needle in a haystack at this point, but you never know," Breanne said.

"Somebody may see it and not know what it is. So the more it gets out there, the more chance we have of this arm showing up again."

With a report from CTV Vancouver's Maria Weisgarber