Only a few minutes later did it occur to me that it might have been the Google car. The direction it went is a maze of dead end streets, so I knew it would have to come back along the road at the corner, which is the only way out. I went out front and looked down the block, and just a few seconds later I saw the car go by. It was one of the Suburus with the green doors.
It's too bad I wasn't in the yard when it first went by, and didn't get out soon enough to walk down to the corner when it came back. I've always wanted a Google Street View picture of me with my face all blurred to use for an icon. I'll keep an eye on Google Maps for the next few days to see if they upload new views of the neighborhood. If I'm lucky, there could be a very distant view of me standing in the street watching the car go by down at the corner. That shot might get discarded, though, as they already had the view up the block they'd taken on their first pass.
I'm really disappointed that I wasn't out there when it first came up the block, though. I might never see a Google camera car again.