Many times, need to probe differents executions plan for the same statement where perform tuning. It is a good practise flush the previous plan before. You can flush the plan from the cache with DBCC command. This testcase is on SQL Server 2012, it works on 2014 too.
First, locate the sentence what you want flush and its plan_handle, you can do it with the following query;
SELECT PLAN_HANDLE, B.TEXT FROM SYS.DM_EXEC_CACHED_PLANS CROSS APPLY SYS.DM_EXEC_SQL_TEXT(PLAN_HANDLE) B WHERE TEXT LIKE N'%SELECT COUNT (*) FROM MY_TABLE%'; -- HERE YOU MUST SPECIFY YOUR QUERY OR SUBSTRING
Second, with the plan_handle got, execute the DBCC command
DBCC FREEPROCCACHE (0x060005001D724F342057CE2B0200000001000000000000000000000000000000000000000000000000000000);
If you execute the query from first step, it returned nothing.
HTH – Antonio NAVARRO