Which is wrong, as I have documents in that folder and running same query for different folder returns proper result. Another strange thing is that I cannot get this folder: following query also returns No items found:
Can you please specify which Alfresco version and indexing subsystem you are using? How large is your index? Would it be possible to attempt a full reindex to see if it was just a hiccup? If you are using SOLR, have you checked the SOLR administration page for indexing errors and / or performed a REPORT action?