I posted a photo to my own Facebook page. Five hours later I deleted it. I hit "delete" and got message saying it was deleted. Others and myself could not see the post. However the next day, about 13 hours later, someone saw the post and screen shot it. How could that post still have been visible to them a day later when it had been deleted and was not visible to others, or to me? Can this happen - can there be a delay that long in the posting being deleted?
No, when you delete a post, it get deleted from your Timeline and no one can see this including you.
However, it might not always be instant as sometimes there is a delay in synchronizing between servers.
But this page claimed that,
You’d hope that by clicking delete, your content is permanently removed. Apparently, that’s not quite the case. New evidence suggests that Facebook might not really be deleting the posts you think you’re getting rid of. In fact, sometimes these deleted Facebook posts are reappearing.
Another possible scenario is that user X has their newsfeed open and this post is displayed. Let's suppose that X leaves the room having their pc on. Then you delete your post. After a while, X comes back to their pc. The post is still displayed unless X refreshes their browser. So this is another way that this could happen .