Are you asking on how to search through your own local data from a instance you took offline?
Lemmy Support
Support / questions about Lemmy.
Not local data, question is meant from a regular visitor point of view (not necessarily an instance admin).
I'm not sure if there is a way to quickly find this. The best bet is probably trying the bigger instances, and seeing if it's accessible through them.
You've made me think now: it might be a nice project for a some instance admins to flag when an instance they had received posts from goes offline. (I should probably check what I have from feddit.de!)
View the community that had that post from that instance on other instances. Should still be there, right?
What are the steps to discover it knowing ONLY lets say "lemmings.world/post/10530999" and nothing else. If that is not possible, then knowing title "Dead Lemmy instance, how/where to find backup of the post that was on the offline instance?" and mentioned URL, while not knowing parent community name or the instance from which the post originated.
Search by post, paste title, make sure you're searching all communities and not just local.
Or paste the URL in the search.
If you know the url, that can be put into the search on instances too.