I always carry two tubes with me. No way do I want to be playing with patches on the road! (Tho just in case, I carry a patch kit as well!) But don't you still need to find the puncture in the tube to determine the to figure out what caused it in the first place? Kind of disconcerting that I doubt I could have found the puncture and therefore the cause of the puncture out on the road.

Have you ever had a difficult time figuring out where the puncture was so that you knew where to look on the tire?