There's nowhere that you should see exposed foam. It would be temporary if you did while waiting for a part to be assembled later. Most often you have foam + a micro slurry + at least 2 layers of fiberglass + more micro and then paint. The foam is well protected.
With that said, and back to the original 'bulkheads' topic, I HAVE seen exposed foam on flying planes (albeit rough-finished) within the inside cutouts of bulkheads. A fix is to fill with 'micro'.
You don't want to let fuel get near foam, which is another topic...