Share a photo On your computer, open Google Maps. In the top left, click Menu Menu and then Your contributions. Choose Photos. Find the photo you’d like to share. In the top right, click More More and then Share.
Picture is from 2011 and was originally hosted on Picasa (but I'm pretty certain it was never shared publicly) and I don't have a Google Plus account. If I go to the picture itself on Photos, there's no sharing/privacy controls, so I'd assume it is private.
The wording on the email makes it even worse, as if I had intentionally done something overnight to share them on Maps.
As far as I remember, I've never used Panoramio (as a comment above suggests to be the cause). I'd agree that this seems limited to some specific circumstances.
Can't remember the exact name of the website, though.
For now, I'll go with fake news.