Searching for a community by its ID seems to be broken on feddit.org. To reproduce:

• Go to https://feddit.org/search
• Change Type: “All” to “Communities” in the drop-down selection box
• Put “!test@sh.itjust.works” in the search input box
• Click the Search button

No results are found.

On other Lemmy instances, I have seen this type of search work.