Caught Masturbating

Years ago I took a summer job in California and would occasionally walk to abandoned areas nearby the house I was staying in to masturbate outside, but taking my bike to go far enough away that I wouldn't be seen, or known if I was seen. One area seemed like an unfinished project with various levels of concrete layered on each other with lots of dirt and overgrown areas on it or nearby, possibly a intended skating park. I did this occasionally for several weeks, maybe 1-2 times a week, when on one occasion I was laying down on my side and taking a good wank I heard some girlish tittering and gasping nearby. Obviously some teens had seen me, but I looked around and could see no one or anything obvious they could be hiding behind. I quickly composed myself and hopped home on my bike, taking some circuitous routes and looking around thoroughly so I knew I wasn't followed. That spoiled my cumming that night, I jerked off in bed but that wasn't as satisfying. Perhaps a month later I was at a mall and I heard someone say something in my direction, and saw a girl directing her friend's attention toward me. Again, I quickly left the area figuring she recognized me from that time in the dark. I was more careful in the future and I'm sure we never saw each other again as I've never been back to that city.