With Ektron 8.5, it is possible to search recursively using the API. This article details how to accomplish a recursive search.
To search recursively using the Search 8.5 API, one of the following Search Properties should be added to the query:
If the folder ID path to the folder to start the search is known, use the folderidpath property, with the search term containing the folder path beyond the "0" root folder. In this example, folderid 104 will be searched, along with any folders under 104. Content in folder id 14 will not be searched. (Note: Do not specify "0" as a search term for this property. If you would like to search the entire site, do not create a property for folderidpath, since the entire site will be searched by default.)
Property = "folderidpath", SearchTerm="14/104"
If the path to the folder to be searched is known by name, then use the foldernamepath property, starting with the first folder after the root folder, as below. This will search all content within the "recurse" folder, along with any subfolder underneath "recurse".
Property = "foldernamepath", SearchTerm="Book Store/recurse"