That decision sparked a 10-hour search and rescue operation and though police say it will end up costing thousands of dollars, they are praising Mr Harrex for staying put.
He had gone deer hunting on his own but had told his parents of his plans and they expected him back before dark.
When his cellphone battery went flat he was unable to tell them of the fog and his revised plans.
He left his motorcycle and the 10-pointer stag he had shot and walked down to Junction Hut.
About 11pm, his parents contacted Alexandra police and a search and rescue operation involving 10 volunteers, three police officers, two St John ambulance volunteers and the Otago Regional Rescue Helicopter was launched.
''We thought that wasn't right [that he hadn't returned] and so we swung into action,'' his mother, Desley, said.
''It's all a bit fuzzy after that.''
Central Otago sub-area commander Senior Sergeant Ian Kerrisk said police were about to ramp up the search yesterday morning by sending more teams into the area when, ''just after 9am, the hunter made contact with his family saying he was safe and well''. Mr Harrex said some Dunedin hunters, who had a working cellphone, arrived at the hut about 1am and together they went out to find reception. They could not find any and because it was foggy, they returned to the hut and waited until morning.
Because he was an experienced hunter, he was well equipped and knew the area. However, Snr Sgt Kerrisk said the concern was that he might have had an accident and needed help.
''It's a significant search that was undertaken but when someone's safety is at risk then our role is to find them and we used the resources that we needed to to do that.
''There will be a cost and that cost will be in the thousands of dollars ... but we think of safety before money.
''He did the right thing by staying at the hut rather than trying to walk out.''
Mr Harrex said he was a bit embarrassed but thankful for all the people involved in the search.
''I knew people would probably panic but I didn't really want to cause a fuss.''
He plans to return today to retrieve his motorcycle and stag.
