MOre than likely on "that" part of the lake, it was just folks out using there boats. Not sure of any clubs that "might" be racing. Now if you were talking in between the bridges on any given weekend or week night in the Ap-sept area, then it could be a race. As that is the most common area for races.
MANY years ago off of what is now David E Brink park in Kirkland, Neptune sailing club owned the land and had C-lark, lighting and Laser races in the northern part of the lake.
She drives me boat,
I drives me dinghy!