When I search a project or theme I know exists, either nothing comes up or it says nothing found. I hope this is patched soon!

Scratch's search engine is currently broken, and all we can do is wait for it to be fixed.
Unfortunately, no one seems to know what's causing issues or when they will be fixed.
This affects everyone on Scratch, so the Scratch Team is aware of the situation.

For now, you can type "site:scratch.mit.edu (search query)" into a search engine like Google to work around this bug.

This also affects the Explore page, since that's internally based on Scratch's search engine.

Thank you! I guess now it's just a waiting game!