Hello sexymum,
It is possible to get set-in stains out of clothing even after they have been dried.
Dawn detergent is great for getting these types of stains out.
Take the shirt and place the detergent directly on the stain.
Allow it to soak in to the stain for a few minutes.
Wash the shirt as you usually would.
Let it air dry and then check to see if the stain is out.
Goop is another product you can try. Follow the same instructions as above using the Goop instead of Dawn.
Repeat steps if necessary.
Mrs. Clean