it's very possible it was deleted due to having poor art quality, or to closely looking like underage porn. Those are the most likely reason a post would be deleted, and since you said you made it yourself it's not likely to have deleted due to being a duplicate. I also think self-uploads of your own art is looked down upon but don't quote me on that.
If you haven't cleaned up your browser history or cache you can probably still find it nestled in there somewhere. It's a chore but you should be able to dig it up most of the time, even if the post is absent on the site's upload history