Looks like I've been hacked or something since an image of a hockey goalie [I've never posted a matching hockey image on this blog] replaced my thumbnail from my post yesterday - it looks like it was only on the mobile version of this site and the correct image shows up when I click on the post.
I don't think I was imagining things - but after fretting about it on the way to work, then the thumbnail reverted back to the original image.