It was posted on Twitter yesterday morning, then on Derpibooru shortly afterward.
Now this is just an assumption (based on my own experiences), but most artists publish their work soon after finishing it, and it's unusual for an artist to sit on a finished commission for more than a few days, especially if it didn't take long to create (like this YCH sketch)
The commissioner is listed as "someone from Discord," which means he's still around but trying to remain anonymous.
I'm just glad to see that he hasn't entirely quit the fandom.
Am I the only one who wants 2k to return as well?