As a fellow stickler, you can sometimes find these works at the cave entrance, but time tends to be less kind to works that are less protected.

I personally know of several sites in North America where the works are on an open cliff face, but also continue into the nearby caves. I’ll not be specific with locations, because people have vandalized a few of the sites.

But yes, the deeper into the cave, the more likely that such drawings have survived to modern times.