In this case, it must be a bug of some sort, because all of the images were uploaded when no post was open. I was working only the in manage media area and uploading everything at once en masse.
It would seem I have the option either to delete my images and try again, which would be painful, or remove the link back to parent in the image attachment page title. For now I’ve removed the link, but I’d still like to resolve it without having to delete my existing work to see if I triggered a bug while uploading the first time around.
