How do I protect autographs on a t-shirt from fading?

My 4 yr old daughter got her Kasey Kahne t-shirt signed by Kasey, with a black Sharpie brand marker, last night at a local dirt track, and being a 4 yr old, she got some of her drink on the shirt and it needs washed. As much as the autograph means to her, I want to protect it from fading in the wash, and her to still be able to wear the shirt as well. Is there a product out there that can be sprayed on the fabric to keep the ink from fading?