Ditto, except it's kbin.social in my case rather than lemmy.world
I probably would have never read this story if it only existed on kbin
I would presume the instance is important here?
That can be the case, sometimes issues with federation can cause threads to get lost across instances, and a new instance may not get all the existing threads on a pre-existing magazine.
However, it looks like both your account and this magazine are hosted on lemmy.world - since you're both on the same instance, you should have been able to see the older posts on this magazine. (Note: magazine is the kbin term for lemmy communities - i prefer it as the term community can be ambiguous). I've never used lemmy proper so am not sure how that works, but on kbin you can view the older threads on a magazine quite easily.