This happened years ago. I washed my gi with other clothes, grabbed it out of the dryer, and rushed to class. Half way through class, I got up from taking a roll and saw a pair of MY underwear in the middle of the mat!!! It must have been stuck inside of my sleeve and it flew out when I rolled! I snatched it up and hid it in my bag. Luckily, I was partnered up with another woman and we had a good laugh over it. I don't think sensei or any of the other guys saw what happened and we didn't tell them why we were laughing.