He was transported to a private medical facility where he was declared dead on arrival by the doctor, and then transported to a government hospital for post-mortem on Friday.
"The emergency medical officer examined him. He did not find any signs of life and hence declared him dead," Rajendra Kumar, the hospital's medical superintendent, told AFP on Sunday.
The doctor said police were informed and the body was placed in the morgue freezer until his family arrived six hours later.
"When a police team and his family came over to initiate the paperwork for the autopsy, he was found alive," he added.
Rajendra Kumar said the 45-year-old was undergoing further treatment but was still in a coma.
"This is nothing short of a miracle," he added.
An investigation was under way to determine how the doctors mistakenly declared him dead.