No, absolutely not. By far not all works of Johann Sebastian Bach are preserved. The most famous Bach Scientist in the world is Professor and Bach Author Christoph Wolff. He estimates, that only ten percent of Bach's compositions made it into our time today. If the nowadays 1,128 works are ten percent of the overall work of Bach, it could be true, that once there were 11,000 music pieces existing back then.
With 11,000 created works in the whole lifetime of Johann Sebastian Bach, and that is without question, he would not have been just one of the best composers and musicians of all times, but one of the most productive too. If not the most productive by far.