I can barely let boys off the hook about this who haven't been warned once before. We talked about it already. If you can't understand that your excretions don't belong on a reusable towel, then I don't know what to tell you. Why would you want any evidence left over? It's because boys are disgusting idiots. Take this boy for example. He was already warned about this once. This is the second time they had to talk to him about it. It's not like there aren't tissues around. It makes me sad for the male species.
I'm sure that Justin Bieber towels and My Little Pony towels would be bad, but wouldn't making him have to hand clean his own towels be worse? That's what he should have to do. Make this kid clean up his own filth.