fixative for fabric pastels?

A friend made me a tshirt with a nice design using what he called "fabric
pastels". When I folded it to bring it home, the colors smudged a little
onto the other parts of the shirt that are not supposed to be colored.

I am afraid to wear it or wash it because I don't want to lose the design.
I've called the fabric stores and the craft stores and they said that the
colors should not be rubbing off, unless he didn't wash the shirt first,
which is a possibility.

Does anyone know if there is a spray or some kind of fabric treatment that I
can apply to the shirt? Or any other advice to help me keep the colors
from coming off?

Thanks!

Pat