This incidence happened fifteen years ago and you must now move on. Perhaps you could talk to the person (if this person remembers at all, which is very doubtful) concerned and 'clear' your conscience. With your present attitude of guilt (which coming from an objective viewpoint is so totally unnecessary !) you will eventually self-destruct and ruin you future as well ! Stop being a VICTIM. Get over it, it's a non-event now :-))