Missed lucene index hits

i index one large database overview (text fields only) on which the user should be able to search (below in the indexFields method). This search was previously performed in the database with the ILIKE query, but was slow, so now the search is performed by index. Hovewer, when I compare the search results with the db query, and the results that I get when searching for the index always always have fewer results when searching by index. I'm not sure if I am mistaken in indexing or in the search process. For me, everything seems to make sense here. Any ideas?

Here is the code. All tips were appreciated!

 // INDEXING
StandardAnalyzer analyzer = new StandardAnalyzer(
                Version.LUCENE_CURRENT, stopSet); // stop set is empty
        IndexWriter writer = new IndexWriter(INDEX_DIR, analyzer, true,
                IndexWriter.MaxFieldLength.UNLIMITED);

        indexFields(writer);
        writer.optimize();
        writer.commit();
        writer.close();
        analyzer.close();

private void indexFields(IndexWriter writer) {

    DetachedCriteria criteria = DetachedCriteria
            .forClass(Activit.class);

    int count = 0;
    int max = 50000;
    boolean existMoreToIndex = true;

    List<Activit> result = new ArrayList<Activit>();


    while (existMoreToIndex) {

        try {
            result = activitService.listPaged(count, max);
            if (result.size() < max)
                existMoreToIndex = false;

            if (result.size() == 0)
                return;

            for (Activit ao : result) {
                Document doc = new Document();
                doc.add(new Field("id", String.valueOf(ao.getId()),
                        Field.Store.YES, Field.Index.ANALYZED));
                if(ao.getActivitOwner()!=null)
                    doc.add(new Field("field1", ao.getActivityOwner(),Field.Store.YES, Field.Index.ANALYZED));
                if(ao.getActivitResponsible() != null)
                    doc.add(new Field("field2", ao.getActivityResponsible(), Field.Store.YES,Field.Index.ANALYZED));

                try {
                    writer.addDocument(doc);
                } catch (CorruptIndexException e) {
                    e.printStackTrace();

            }
            count += max;

 //SEARCH
    public List<Activit> searchActivitiesInIndex(String searchCriteria) {
    Set<String> stopSet = new HashSet<String>(); // empty because we do not    want to remove stop words
    Version version = Version.LUCENE_CURRENT;
    String[] fields = {
            "field1", "field2"};
    try {
        File tempFile = new File("C://testindex");
        Directory INDEX_DIR = new SimpleFSDirectory(tempFile);
        Searcher searcher = new IndexSearcher(INDEX_DIR, true);

        QueryParser parser = new MultiFieldQueryParser(version, fields, new StandardAnalyzer(
                version, stopSet));


        Query query = parser.parse(searchCriteria);

        TopDocs topDocs = searcher.search(query, 500);

        ScoreDoc[] hits = topDocs.scoreDocs;


        //here i always get smaller hits lenght

        searcher.close();
    } catch (Exception e) {
        e.printStackTrace();
    }


}