Documents & Files Search Index not working for programma

Hi,

When I upload & publish a document through Sitefinity Backend, the search widget returns the uploaded document.

When I do the same pro-grammatically, as I have a form that the user will fill in through a front-end page & will upload a document from there which i then upload & publish to the Document Library of Sitefinity through custom code, the search widget does not return that document(.docx, txt files).

When I manually unpublish the document uploaded programmatically & re-publish it through Sitefinity Backend, the document then appears in the search index results. 

Why is that happening? I am uploading the document through normal procedure & its even in published state, why is it not being returned by Search Index when I upload it through LibrariesManager api through custom controller code.

Any help would be appreciated, we are using out-of-the box search service of Sitefinity. Sitefinity version is 8.2

Thanks.

Following is the code I am using to upload the document programmatically - These uploaded document are not being returned by SearchIndex - When I manually Unpublish/Republish them they start appearing: 

 private readonly LibrariesManager _librariesManager = LibrariesManager.GetManager();
Document document = _librariesManager.CreateDocument(Guid.NewGuid());
_librariesManager.Provider.SuppressSecurityChecks = true;
DocumentLibrary documentLibrary = _librariesManager.GetDocumentLibraries().Where(d => d.Title == "xxxx").SingleOrDefault();
document.Parent = documentLibrary;
string Title =  "xxx"
string docTitle =  "xxx"
document.Title =  "xxx"
document.DateCreated = DateTime.UtcNow;
document.PublicationDate = DateTime.UtcNow;
document.LastModified = DateTime.UtcNow;
document.ApprovalWorkflowState = "Published";
document.UrlName = "xxx"
document.MediaUrl =  "xxx"

_librariesManager.Upload(document, file.InputStream, Title.Substring(Title.LastIndexOf(".")));
_librariesManager.RecompileAndValidateUrls(document);
_librariesManager.Lifecycle.Publish(document, new CultureInfo(cultureName));
//_librariesManager.Lifecycle.CheckIn(document);
_librariesManager.SaveChanges();
document.SetWorkflowStatus(_librariesManager.Provider.ApplicationName, "Published", new CultureInfo(cultureName));

//For Publishing Live document
// var bag = new Dictionary<string, string>();
// bag.Add("ContentType", typeof(Document).FullName);
//  WorkflowManager.MessageWorkflow(document.Id, typeof(Document), null, "Publish", false, bag);