I think there's a bug in the way WPSC behaves:
- When in Preload mode, when a post is published it gets cached indefinitely (unless updated).
- When that post is changed from "published" to "draft", the cached version is NOT deleted. Therefore, the post remains public and accessible - even though it no longer is.
- The only way of getting rid that post online, is to manually delete the cached page.
I tested this on a clean WordPress installation to verify this is indeed what happens regardless of my system.