When I was about 16 I went to a sleepover at a friends house. There was about twelve of us altogether, about five girls and seven boys. I positioned myself on the chair in the corner, most of the others got into their sleeping bags and laid on the floor.
A girl friend called clare chose a spot on the floor in front of me on the floor. I had always fancied clare so was watching her closely as she got ready to get into her sleeping bag. She sat on the floor, then wiggled into her sleeping bag. Almost immediately I could see the outline of her arm move down to her groin area and her hand resting between her legs. Her hand then started moving quickly in a rhythm. I was hoping she was doing what I thought she was, but dismissed it because there were so many of us in the room and the light was still on. Her hand movement carried on for a few minutes, then she stopped, her hand slid back up her body and out of the sleeping bag. She then put her fingers upto her nose and was smelling them, although she done it in a way to make it look like she was itching herself just under her nose. After a few sniffs the hand went back into the sleeping bag and straight back between her legs and the movement started again. Within a couple of minutes she suddenly let out a gasp, so loud everyone in the room stopped talking and looked at her, although it didn't seem to bother her.
No one else seemed to have noticed what she had just done except me, and she didn't seem to have noticed I had seen her. She then turned onto her side and started to join in the conversaion like nothing had happened.
I couldn't believe what I had just seen, and have got myself off probably hundreds of times to that memory. All true I promise.