Public posts behave differently from stories
Unlike stories, public posts do not disappear on a fixed short timer. They usually remain visible until the source account deletes them, archives them, restricts them, or changes who can view them.
That means a missing post often needs a different explanation from a missing story. The profile may still be public while one specific post changes status, which is why post-level troubleshooting should not be treated as the same problem as story expiry.