You can try playing with the parameter simpleto see if your queries matter. According to the API link (half of them are currently unavailable), it makes the results the same as for the website:
(optional) This parameter specifies whether or not to enable advanced search queries (additional information). When set to false, the API search behaves the same as a search on Scribd.com . If set to true, API search allows you to use advanced queries that contain filters, such as the name: "A Tale of Two Cities." Set the value to true by default.
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