Portal for ArcGIS 10.3 is unable to find feature services published to the portal or added as an item when the check box 'Within map area' is checked in the 'Search for layers' option.
Duplicate of BUG-000096966: A layer without a defined spatial extent will not be returned when using the ‘Within Map Area’ filter inside the Map Viewer. Confirm that an extent has been set in the Item’s detail page (under Settings). Documentation link on editing settings (including Extent) found here - http://enterprise.arcgis.com/en/portal/latest/use/item-details.htm#ESRI_SECTION1_4ED3645CEE1B4FA7A192FF0D5583524A