Im glad it was resolved and while they were incredibly unprofessional themselves even as a minor artist, I can't help but be really put off by your quickness to take all money back including the money for completed work, and even after changing your mind to thankfully do the right thing and pay the artist, to state they didn't earn that money.

Hopefully all this was a good learning experience and hopefully things won't go this way in the future. But if you want a short deadline in the beginning, I would def state the date you expect/want it to be completed by in the beginning in the future.