As long as the plan is still loaded into the proc cache, you can somewhat use the DMV's for this. If it wasn't run since the last cache flush or restart of SQL Server, you have lost it and won't be able to tell at all, even with a SQL Trace:
select db_name(eqp.dbid) as [DBName],
object_name(eqp.objectid, dbid) as [ProcedureName],
eqs.last_execution_time
from sys.dm_exec_cached_plans ecp
join sys.dm_exec_query_stats eqs on ecp.plan_handle = eqs.plan_handle
cross apply sys.dm_exec_query_plan(ecp.plan_handle) eqp
where objtype = N'Proc'