DragonsAreSexy said:
https://i.imgur.com/jtd1bBG.pngPlease and thank you!
I didn't find this, but I think it's worth mentioning. Most insigned drawings, and specially sketches, these days seem to be produced by 4chan, and just about every fandom and/or board and/or general thread has its own Booru.org site.
In the same vein, some of 4chan's archival sites allow you to search by picture, most notably desuarchive.org. The only downside is that it's by hash, not image similarity. Still, you can try searching for image width and height, and guess filenames or some other creative way. Also, if your search returns nothing, pay attention to the message it gives. "No results found" is obvious, but you might get some other error message for whichever reason, and searching again might yield results.
Updated by anonymous