This is very possible, post can be deleted at any time as long as the moderator got to discover such, irrespective of the time it had been posted without being noticed, sometimes it takes them a while to check on posts and found some to be off topic, or worth deleted and they take every necessary action immediately as they got to know, what makes some get noticed as quick as possible is when the moderators received a report concerning the post, this also make the action fast on deleted posts.