Mr Shaw was unable to smash his way through a door to save him.
Mr Sim and other family members were oblivious to the tragedy until a news photographer who was at the birthday party was suddenly called out.
He said emergency services at the scene initially feared Ms Sim may have been buried alive along with her partner.
"It was a tremendous tragedy to us ... he never had a show, you know ... Hugh never had any opportunity to get out,'' Mr Sim said yesterday.
"It was just boom, it hit the back of the house, and he was in the bedroom.''
His granddaughter, who gave birth to Mr Biddle's daughter Zekaiya three months later, was left devastated.
"It took her a long, long time to get through it ... emotionally, it affected her quite badly.''
Mr Sim believed authorities should have recognised the landslide danger posed by that day's unusually heavy rainfall and evacuated the houses under the escarpment.
He was aware of previous landslip issues at the property and a picture on Mr Biddle's Facebook page appeared to show debris that had come down behind the house.
"If they'd said we'd like you to come out of there just in case something was going to happen, I think Hugh would have survived,'' Mr Sim said.
He complained to Whakatane District Council days after the landslide and remains hopeful urgent action will be taken in future events.
Since the tragedy, stormwater works at a subdivision above the western end of the escarpment has reduced the amount of water flowing over its edge and affecting stability.
The council was also identifying areas most at risk from landslides and was putting in place measures to reduce threats, public affairs manager Ross Boreham said.
Residents threatened by slips were also being asked to look out for warning signs and take action if they had concerns, but Mr Boreham wasn't aware of any evacuation protocols.
Speaking on behalf of her daughter, Annemarie Sim told the Herald how every day since the landslide was a struggle for Cherize, now 18.
"Things would be much different if he was still here, her daughter would have a dad and it's hard for her to think about that everyday when she looks at her daughter because she looks just like her dad - she smiles like him and laughs just like him.
"She's a beautiful little kid and he would just love her to bits.''
The family also believed evacuations would have saved Mr Biddle, she said.
"There was already a landslide in the same place in January of that year and another one just the week before.
"There were trees that people said needed to be chopped down that hadn't been, so they definitely should have done something.
Realistically they should be answerable to something because his daughter is left with no dad now.''
- Additional reporting Morgan Tait
