As part of the search, police and search and rescue teams searched bush areas around Waitākere Hospital, Central Park Drive, Tui Glen Reserve and Henderson Creek.
Today, an inquest before Coroner Morag McDowell was heard in Auckland.
She said Tan's disappearance was appropriately managed by clinical staff at the hospital, "but I do have some questions of the police search".
The police search included the Eagle helicopter, Senior Constable Paul Herman told the court, and added when Tan was found there was no evidence of foul play.
Detective Sergeant Steve Salton said police treat missing persons cases as seriously as murders, but a risk assessment is conducted for each case to determine how vulnerable the person or public may be.
He said there was no indications Tan was suicidal and while he had mental health issues he was described as "resourceful" which led police to lower his risk assessment.
However, the information was not recorded and Salton said "a lot more info is recorded now" for missing people.
Coroner McDowell questioned if there would be a benefit to police by having a recorded assessment to document changes in the risk assessment.
When further questioned by the coroner, Salton admitted the police response to Tan's case "would be different" today compared to 2014.
He said police processes have changed, which include bigger teams working different hours and more communication with mental health staff.
However, he said: "In this situation he ran away, he didn't want to be there."
Tan's family and friends, including his sister Cindy, questioned Salton over why police lowered the risk assessment because of the "resourceful" label despite Tan "acting out of character" and going missing in adverse weather conditions.
"Although he was not dangerous or suicidal he was very vulnerable," one of Tan's friends said.
Salton also spoke of the five missing persons cases police had during the past weekend, and the death of Michelle Simpson.
Simpson was a mentally impaired woman who wandered off and got lost in Waitākere, sparking a frantic three-day search that drew on hundreds of volunteers.
Her body was found just 600m from the home she shared with parents Elaine and Michael on November 14.
The risks factor in Simpson's case was "quite high", Salton said.
The detective also added police are not influenced by whether family and friends are also conducting their own searches as Tan's had.
When assessing the artist's bank records, Salton said it became apparent Tan hadn't been using his bank account, leading to an increased risk assessment.
He said missing persons cases were assessed continually based on information becoming available, including on social media pages.
Coroner McDowell addressed several of Tan's family and friends in the court and apologised for the delay in reaching an inquest into his death.
"It has been a very long journey for you," she said.
Tan was internationally known for his paintings of New Zealand's wilderness and suburbia.
Family and friends had looked at his paintings for clues about his whereabouts at the time.
"He was clearly a very talented and gentle young man," Coroner McDowell said, while later reserving her findings.
