No pain means one of two things: it's in his bladder, or it went back into his kidney because it was too big to go through the ureter.
If it's too big, it may sit in the kidney for a while or it may try to come down again.
Not fun.
I've passed about 3-4 in my lifetime and have had two others "shocked" to pieces. The bad thing about stones is that there is no easy way to get rid of them. You pass them, they hurt. You get them shocked, they still pass and hurt. You let someone go up "there" to cut the big pieces up, you pass them, they hurt. Or, you have to have a big cut on your back through your kidneys to get them out.
It all hurts, even with good drugs.