Well, seems like you really had no stones this time. But how do you feel? Did you feel any pain before this flush?
Still I am not sure that this is your first "no stone" flush meaning that your liver is all clean now.
You see, I have this idea and so far has not been either denied or supported here, but it makes a lot of sense to me as I read more and more reports from different people about their first four flushes.
So my idea is that liver has several segments (3-4) and during first flushes those segments empty from stones one by one. It explanes to me why every flush (especially first three or four)is so different. And I am pretty convinced that one gets first real picture of what was really in his\her liver only after three four flushes done in two weeks or so intervals. (At least three or four first flushes, cause in some cases it can take more flushes for each segment to empty).
So in your case I would suggest to flush a couple of times more.