Once you have completed your insert, but before disposing of the temporary table you could try using something like
SELECT COUNT(*) FROM [temp_table] WHERE ComboKey NOT IN [master_table]
Where the ComboKey is some combination of key values that will uniquely identify the record you have tried to insert.
You are expecting a value of 0 to be returned. Any non-zero return indicates that you didn't insert everything.
Overall you might be better off using transactions ... have a look at SQL Server Transactions and Error Handling