Searching in File Collection Hierarchy

I am extensively using File Collections to catalog folders which reside on various drives and at various directory level depths. The File Collections themselves have a simple one-level hierarchical structure. For example:

[Assets Collection]
    [Low Res Assets]
        Cats-1-Folder     (this could be say on C:\Cats-1-Folder)
        Cats-2-Folder     (this could be say on N:\Media\Animals\Public\Cats-2-Folder)
    [High Res Assets]

Starting at the top collection [Asset Collection], I am trying to find all folders in the Sub-Collections which for instance include CAT. So in the example, I should get Cats-1-Folder, Cats-1-Folder, Other-Cats-1-Folder, Cats-and-Dogs-Folder.

If instead of using collections, the structure be a normal directory hierarchy, I understand that using advanced search with a location match set to something like NOT (*\*\*) would do the trick. However, when applying the same logic to collections, the search seems to use the physical path to the respective folders, instead of the path within the File Collection.

Is there some clever way to restrict the search to the collection path only and not the physical path using advanced search, or is this a case that can only be solved by scripting (Using FSUtil.ReadDir)?

Applying labels to the folders in each collection might be a way to do it without scripting. Then you can search on those labels instead of by location.

But you would then need to keep the labels and collections consistent. (Unless you switched over to using labels entirely, and ditched the collections. That may or may not make sense, depending on if you're using the collections for more than searching.)