I have searched using Omnisearch in aem 6.2 for try to get a result from my folder. My folder name is "12345". Omnisearch is not getting the assets in folder, but it works fine in folder which has only characters or alphanumeric.
It does work.
I added an asset "12344.jpg" and I do see the asset when I do an omni-search.
Please check the Location:<...> in the search filters. If it's pointing to Projects, it may not work.