Flushes vary. My first and third flushes produced no stones, but I've gotten over 10,000 out in total along with parasites, worms and candida. If it's in there it will come out eventually. You did nothing wrong.
I very seldom use anything to soften the stones. Occasionally I'll take some apple cider vinegar, but less than the prescribed dosage.
Even if you didn't see any stones, your body gets rid of other toxic junk making every flush a successful one. :)