What to do about a commission that I hate?

I recently commissioned my friend, who is the best artist I know, to draw a small design on the back of my new phone case. The design would have been in the shape of a relatively small triangle in the center of the case, but I didn't get what I asked for. They blew up the design inside the triangle to the entire case, so it didn't retain its shape, and also got rid of a sticker and another design that I already had on the case. They also told me when they accepted the commission that they would go over it in a clear varnish to prevent it from fading, but they didn't do that. They told me it would be done in a week, but I didn't get the case back until a full month later. The quality is also really low; I wasn't expecting perfection, but even I, who hasn't drawn in years, could have done better if given 20 minutes - and I'm contemplating doing just that. I'm tempted to wash it off and just do it myself or pay my other artist friend to do it, but I see the person who did it every day, and they would definitely notice if I replaced their work. I don't want to hurt their feelings, but I really hate what they've done to my phone case. Should I wash it off or just deal with it?