The man’s ute was parked on State Highway 1 outside Tinwald's Sims Bakery about 11.20am last Thursday.
An eyewitness suggested the pie then became the man's comfort food.
"He was eating his pie while he was waiting for the fire brigade to turn up," a bakery staff member said.
"He seemed okay."
Ashburton Volunteer Fire Brigade chief Alan Burgess said the cause of the fire could not be confirmed, although it was suspected to be a bird’s nest.
"It’s that time of year again," Burgess said.
A discussion with the ute owner revealed he lives in a rural part of the Ashburton district.
Firefighters extinguished the blaze, but the ute was badly damaged.
The flames engulfed the front and the inside of the cab. But the tools in the back of the ute were saved.
Police arrived at the scene shortly before firefighters and briefly closed the highway, diverting traffic around McMurdo St.