Pinehurst #2 is the only course I have played where I felt in no jeopardy of losing a ball or spending an unnecessarily long amount of time having to look for a ball.
The people that cite Kingsley, Sand Hills, Ballyneal, Old Mac, etc play a different game than me. It is certainly possible to play a round at those course with one ball and I have probably accomplished it at 3 out of 4 of those locations. That being said, pulling it off and it being the norm are two different things. Rarely have I played a round at any of those courses where someone wasn't looking for a ball for some period on multiple holes. Old Mac probably less looking than the others but there are a few places to sure fire lose a ball there... Gorse on 11, gorse right on 15, left on 17 quickly come to mind. The other three all have enough penal rough that if you are offline and miss the generous fairways it may take some searching.