How does Tova ruin a special concert shirt that belongs to Ethan?

Tova is having dinner with Ethan when Cameron comes, and Ethan takes him aside to talk to him. While Tova is waiting, she cleans the kitchen. She does not see any sponges or dishcloths, so she grabs an old T-shirt and uses it to mop up red wine and wash the dishes. When Ethan finishes talking to Cameron, he is horrified that she has destroyed his Grateful Dead concert T-shirt from May 26, 1995.