I recently had a similar experience to you!
My Grandmother was brought up by a William & Lucy Taylor, who she believed to be her Grandparents. (She didn't know who her parents were, and whenever she asked for her birth certificate, she was told she would be given it later).
William & Lucy owned a shop in a small village called Bisley in Gloucestershire.
I was interested in finding out where abouts their shop was in the village, so I posted a message on the village website. The 'webmaster' of the site was interested in the story about my grandmother and referred me to a book that had been written on the history of the village.
I purchased this book from amazon, I had to wait about 6 weeks for it to arrive, but it was well worth the wait.
Looking through the book, I found out where William & Lucys shop was, which had a picture of them (one that my Grandmother had kept and treasured all her life) next to a paragraph about William and their daughter Hilda.
Of course, immediately I started wondering who had given the author that photo?
From this book, I also found out that one of William & Lucys other daughters had married the villiage blacksmith Arthur Davis!
I then found an e-mail address for the author, only half expecting her to reply as the book had been written over 10 years ago.
She replied to me a few weeks ago, saying that she couldn't remember who had given her the photo, but she knew that Arthur Davis' son and grandson were still resident in the village!
All I have to do now, is to find them in the directory and pluck up the courage and drop them a line!!
It really is amazing how you come across information sometimes!