Caught getting a blowjob !

Many years ago , when I was a much younger man , I had a very sexy , hot , busty , horny girlfriend. She was a lot of fun and she was always down for a good fuck ! Sucking my dick with enthusiasm was a great benefit in our relationship. She loved to suck me off and never disappointed me with , '' I am not in the mood , or , not tonight '' Anyway one night we were at her parents house, hanging out and watching TV. I was just having a great time enjoying playing with her big tits and rubbing her nipples when she started to rub my hard cock through my pants. Well I knew what was next and I was ready for a first class , sloppy blowjob , that always ended with her swallowing my load with a smile. She got down on the floor in front of me and , like always, was sucking like a pro. I used to try think about something else so I would last as long as I could. After a few minutes I saw headlights pull in the driveway and she couldn't see that it was her sister coming home. I wasn't sure what to do. Should I tell her and have her stop or just hope her sister would come in the house and go strait upstairs and go to bed. It was not a difficult decision, I chose the latter. LOL ? Then I saw her walk past the window beside me and towards the door. She walked up the three steps and reached out and started to open up the door. Now she was at eye level with me and she stopped and slowly turned around and looked right at me. Again not knowing what to do I was surprised to see what she did next. Where she was standing she could see me and I am sure she could see her sisters head going up and down in my lap. Then she , still looking right at me , got a big smile on her face and got up on her tippy- toes so she could see better. She watched for 15 or 20 seconds and then gave me a thumbs-up and proceeded to go in the house. Soon after that I shot my load down my girls throat she happily swallowed it being sure to lick every drop from her lips and chin. She smiled and got up and went in the kitchen to get something to drink and when she came back she looked out the window and said , '' Wow my sister's car is out there. I wonder when she came home , I didn't even hear her pull in , did you ? '' I can remember saying something like I was a little preoccupied and I didn't notice. I never told her that her sister saw us and I never saw the sister again. I have thought about it many times over the years and I will always remember that smiling thumbs-up. ???