Thorne had returned to his Canterbury farm ahead of the province's Air New Zealand Cup campaign, attempting to recover after the Crusaders' Super 14 triumph.
The 31-year-old told The Dominion Post: "It was the last thing I was expecting.
"I didn't think I'd get any benefit from it. I'd played a full Super 14 and felt taking a break would be more beneficial than playing four more games."
Thorne was feeding hay to his cows when his wife, Kate, told him Henry was on the phone. It was the call he had seldom dared to dream would come.
Thorne has not played a Test under the current coaching regime after being captain for the 2003 World Cup.
"You always hold out a bit of hope but I didn't think they would call on me given what's happened in the last few years," he added.
The All Blacks meet up this week ahead of their Bledisloe Cup tie with Australia in Christchurch on July 8.