ISSUE
There was an issue that item search from a restlet script showed empty results for a specific role used for integration. When the search is executed in UI, results are present but when run through restlet script it shows empty results.
SOLUTION
The issue was with the subsidiary restriction permission issues. The custom role for the integration initially had access restricted to the User subsidiary only. However, when access was granted to all the Subsidiaries under the Subsidiary restriction tab in the role record, the issue was resolved, and the item search displayed the correct results.