The move paid off, and Mr Borthwick and his daughter have been reunited with their precious heirlooms.
On Wednesday night, he posted a photo of the rings and an appeal for information on his Facebook page.
He hoped the post might lead to some information being passed on to police, but the post went viral.
Mr Borthwick said the outpouring of support he received from around the world had left him stunned.
More than 27,000 people shared the post on Facebook between Wednesday and yesterday afternoon.
A further 16,000 people "liked" it, and dozens of people commented on it to offer their support.
A staff member at the Pawn Shop in Christchurch recognised the rings after seeing the post, bought them, and gave them to police.
Mr Borthwick said he would be "forever grateful" to the woman for returning the rings.
He said he was blown away by the reaction the post had generated on social media. "It's pretty weird. I just sent it out to my friends and they said I should make it public so I did, and it just went crazy."
As well as a surge of support from Ashburton locals, people from as far afield as Britain and the United States had shared the post.
"It shows you what the community can do when they get behind something," Mr Borthwick said.
— Ashburton Guardian