Bike Culture shop owner Rob Smail and Rotorua Bike Festival events co-ordinator Kim McVicker were at the car park by Hill Rd when they spotted the bike being put into a car.
"I decided to go and talk to him and said I knew his bike was stolen," Mr Smail said.
"We couldn't believe he was still around. He looked like he was going to do a runner so I asked Adam King who was driving past to stand with me."
He then called off-duty police officer Sergeant Dave Hamilton, who was organising the downhill race, to attend until Rotorua police could arrive.
In explanation to police, Buchs said it was expensive to rent mountain bikes and he had planned to leave the Yeti 575 outside the Outdoorsman before he left Rotorua.
Mr Peers said Buchs had underestimated the mountain biking community.
"It's awesome work on their behalf and it makes our job a lot easier. It's good work from our community, we put it on our Facebook and it went viral. The mountain biking community is a small community and everyone knows everyone."
Buchs, who needed a Swiss interpreter in court, was yesterday granted bail but was later recalled as the occupant of the Rotoma bail address advised she didn't want him. He was instead remanded in custody until Thursday. Police have confiscated his passport.