I always suggest looking at findagrave.com. When I did that I found a headstone photo for Christine Kennedy Bache, identified as his wife. This makes me wonder if there is a stone for John.
You might want to check with the person who submitted the photo of this grave, and ask if they recall a stone for John.
http://www.findagrave.com/cgibin/fg.cgipage=gr&GScid=214...;
Lisa