I search it from the search bar, and nothing comes out. (In Hubzilla 7.0.1)
When I search #^https://zotum.net/item/28daa2ff-a7af-475e-b674-70c043f515fd I'm redirected to HQ page, with latest post in my stream (unrelated) displayed.
What's your reason to put that complete url into the search bar instead of into the address bar of your browser?
Maybe it can be determine in reverse from inreplyto, but i think that would miss some posts.
But would you mind explaining the redirect loop issue?