"I was about 60km into it and revelling in it," he says of the annual event he's taken part in for years and wouldn't miss.
He got off his bike rather than risk falling. His condition rapidly worsened and when his son came back looking for him, Mr Gascoigne's eyes were rolling up in his head and he was barely conscious. His son tried desperately to call emergency services - even climbing a tree at one stage to try to get his phone working - before the truck came along.
"You're on a highway between two centres ... it's not on these days," Mr Gascoigne says about the phone failure.
He said the turn of events on the Northland tour was particularly hard on Aaron because, in February 2013, he was with his father-in-law, Whangarei realtor Michael Springford, when he died suddenly during the Wellington-to-Auckland Cycle Challenge.
Mr Gascoigne is out of hospital now, recuperating at home in Cambridge from what was a life-changing experience. He reckons he dodged a bullet, largely because of his high level of fitness. He'll be back in the Northland cycle tour next year "for sure".
When he was in hospital and saw other stroke victims, "I realised how lucky I was. That driver didn't have to stop, or he might have viewed cyclists as a nuisance on roads where driving is already tough.
"The drivers, they have a job to do, they're awesome with us cyclists, and they sometimes get a bad rap. That guy is someone I want to meet, but I don't know who he is or what company he works for. All I know is that he drives a red truck and I need to shake his hand."
-The Northern Advocate wants to get behind Greg Gascoigne's quest to find the truck driver. If you are the truckie or know who he is send us a line at reporters@northernadvocate.co.nz or call 09 470 2875.