"If you are actually the original author, please do reply to let us know!"

The point here is that even if it's your own work, if it has been published elsewhere, you should cite your own work by either providing a link or some other proof that it is yours. If people can find your photo on another site, how can you prove that it is your own photo and that you have all rights to it? Especially if this photo was published on tumblr in November 2017, which is months before it was made into a post here on Steemit.

I re-post my original stuff that I've posted on tumblr, but I provide a link to the original post so that the readers on Steemit can see that I'm not plagiarizing someone else but rather it is my own work/content.