Spontaneous liver flushing! They should take a sworn deposition from you! :) Cases like this are great arguments against the opinion that the stones we flush consist merely of the olive oil and Epsom Salt
we use to force them out. What do your stones look like? What led you to you determine that they are gallstones?
My speculation as to the reason you are passing Gallstones
spontaneously would be the same as yours, and scarcely more informaed, so I'll leave attempting to answer your question to others.