Well, if you're "rich" and don't mind blowing 50 pts, you can always try the link and verify it's dead.
Also flex your search-fu to make sure it hasn't been reposted... search here can be wonky, so make sure you try the full canonical name, single words, AND the SKU... sometimes a post shows up in one search but not another when it should. Also, sometimes one of those dead posts is actually part of an existing Bundle, and therefore should not be reposted.
Also, the "report broken links" function goes to staff, the "request new link" function messages the author directly instead.
You can always check a user's profile to see when they were last active - if it was hours or days ago, you might want to message them. If they were last active in 2017, yeeeeaah, report a dead post.
Once you make sure the post is NOT in the blog, repost it. There's no blackout period, you can repost right away.