Are you taking pain meds? I have passed stones before, and didn't feel them pass. If you caught something in the strainer, then you need to take what you collected to your doctor and let them determine what it is. Good luck!!!! I have suffered from kidney stones since 1998........worse pain I have ever experienced.......even worse then the deliveries of my 3 children.
Best of luck to you!
It is definately possible to pass a stone this size... I have had over 45 stones, had them blown up, cut out (30 yrs ago before lipotripsy), basketed and passed them. Two weeks ago I passed an 8mm stone. My Urologist has given me Flomax, when I feel a stone I take that once a day and it helps relax the ureter so the stone can pass. This last one was a doozy... it passed the night before I was scheduled for surgery. Good luck. Do get some Flomax.... it has helped me pass the last ten or so.
It could have been due to breakage of the stone in small size which has passed through the ureter. Confirmation whether the stone has passed or not can only be done by an ultrasound KUB (kidney, urinary bladder).
Drink plenty of water and talk to your nephrologist regarding the treatment of kidney stones which include pain killers, trying avoiding taking calcium rich foods. If the symptoms persist then surgical intervention is needed. This includes, ureteroscopy, ureteral stent placement, ESWL and percutaneous nephrostomy.
I suggest you to get an evaluation done from a urologist and discuss the various treatment options.
I hope it helps. Take care and regards.