Jonathan Coppack, 32, raised at least $20,000 in donations for Plan International, an organization that gives medical aid to developing nations, when he and two friends rode their bikes from Argentina to Caracas, Venezuela, three years ago, the Daily Mail reported Wednesday.
Coppack said he is devastated someone stole the $1,400 bike he rode during the journey.
"That bike was my most treasured possession and I feel like a part of me has gone now. I can't just go to a shop and buy another one because it wouldn't have the same memories I have from that bike," he said.
The thief was caught on a surveillance camera using bold cutters to remove the bike's lock before they took it from Coppack's home in Hythe, England, near Southampton.
Hampshire police said they were looking into the incident.