I agree with those who say the best solution is to pick out all the stitches and put it back together right, but if that's too difficult, I wanted to point out that iron-on interfacing will usually come off if you heat it as you did when you applied it. If you can test it first on a scrap of the same fabric. There might be glue residue. If it's t-shirt fabric usually it's the same on both sides, but I'm guessing you have some sort of design that is on the inside now, and taking off the interfacing won't solve that problem.
I have lots (!!!) of experience picking out stitches and want to say that if you don't have good lighting and good magnification and a very sharp seam ripper, now would be a good time to get them. Ott makes more than one version, depending on your budget, so that's one option, but I have been using some Mag-Eyes next to a bright window when the sun is on the other side of the house to avoid glare. You'll be surprised how much easier it is than the same work in ordinary indoor light without the magnifier. Do pick out the quilting from the back because if you slip and make a hole there, an applique is a better option than on the front. I have one where I appliqued a piece of fabric over a hole, and because the backing is a busy print and I was able to line it up, I would have a very hard time finding it even though I know it's there. Good luck!
Editing to add that if you want to match the quilting exactly, try tracing or drawing it before you rip it out.
Last edited by Rose_P; 10-21-2018 at 10:18 AM.