Now the three-year-old has lost his prized possession and his mother Katie is desperate to get it back.

Father-of-two Bryn Peden was tragically killed last March when his motorbike crashed into a tree off Cotter Road near Stromlo.

Before his death he gave his eldest son Braxton his LA Kings hat because it was too small for his head.

Katie said the hat was lost in Sydney Domestic Airport on Monday after visiting her late husband's family on the one-year anniversary of his death.

"It wasn't until we got off the plane in Launceston that I realised we didn't have the hat," she said.

"It's very sentimental to us. Bryn gave it to Braxton because he thought he would grow into it. It's special."

Katie and Bryn had been planning to move from Tasmania to Canberra when tragedy struck last year.

Bryn had made the move first and was working as a cabinet maker with the family business at the time of his death.

"We don't have Bryn anymore," Katie said.

"We just have his belongings. These things are memories for us.

"I'm hoping one day Braxton can look at the photo of him in his hat alongside his dad and he can remember that."

Katie said she hoped the goodwill of people and the power of social media could help her track the hat down.

Already, a number of strangers had approached her to say they had spotted the hat sitting on a desk before the flight took off.

"To get it back would mean a lot to me," she said.

"To some people it might just seem like a hat. But to us it's so much more."

She added that she was still planning to move to Canberra with sons Braxton and Archie, now 20 months, finishing the dream she and her husband set for themselves one year ago.

"We are still hoping to make the move soon," she said.

"It's about giving the boys the best opportunities at life that I can."