Steps to recreate problem:
1. Navigate to: https://moodle.org/mod/data/view.php?d=13
2. Type 'calculated' in search box. Set 'Sort by' to 'Time modified. Press 'Save settings'. Search results show matched items with 'calculated' highlighted in blue.
3. Now change 'Sort by' to 'Author' for example. Press 'Save settings'. Result: 'No records found'