I know this an old post, but I grew up in this area. Remember the store very, very well. Though, it was owned by Gus and Mary Deveareaux (not sure of the spelling). This was the mid-60's. It probably closed as a store in the 70's, but that's just a guess. It's still a private residence.
One of my high school friend is Mary Anne Boyle and she said it was her great uncle that owned the store and she thinks she has a picture of her Grandfather in front of the store when he was young. She said the picture isn't in great shape. If you are still looking for a picture I will ask if she can scan it and email it.
St Augustine is about 25 km from Kingsbridge.