Phantom stains on my son's tae kwon do uniform?

My son takes Taekwondo with ATA, and I'm having an issue with his uniform. I took it out of the washer the other day and hung it on the back of a chair to dry. The bottom of it was dragging on a towel that was on the chair, and now there is this brown stain along the bottom of the uniform top! It almost looks like it soaked it up from the bottom. This isn't the first time it has soaked up unexplained stains while wet, but they normally come out when I wash the uniform. Not this time. I can't bleach it because it has colorful patches and the school's logo printed on the back. HELP! He has a public demo TONIGHT!!!