How to parse query plans to get a count of nested loop operators with unordered prefetch?
This will Work Perfectly®

WITH XMLNAMESPACES ( 'http://schemas.microsoft.com/sqlserver/2004/07/showplan' AS p )
SELECT qp.plan_name, 
       qp.query_xml.value('count(//p:RelOp/p:NestedLoops/@WithUnorderedPrefetch)', 'int') AS operator_count
FROM dbo.query_plans AS qp;


If you prefer, you could use

WITH XMLNAMESPACES (DEFAULT 'http://schemas.microsoft.com/sqlserver/2004/07/showplan')


...and omit the namespace prefix p: from the XQuery expression.