Yep, you should still get stones out. I beleive within 30 minutes of taking the oil is when the stones have most activity of being released from the ducts, so I would think if you haven't thrown up within that sort of time it should be ok. I felt (and would of thrown up if i didnt take ginger) sick 3 hours after taking the oil on my last flush. I sat next to the toilet incase I needed to puke but then relaised i also needed the toilet, and released stones even though i was on the verge of puking all the oil up.