Me da toda la paja probarlo en http://sqlfiddle.com/, pero entiendo que un error en el trigger hace un rollback de la transaccion de ese insert

FOR | AFTER
AFTER specifies that the DML trigger is fired only when all operations specified in the triggering SQL statement have executed successfully. All referential cascade actions and constraint checks also must succeed before this trigger fires.
AFTER is the default when FOR is the only keyword specified.
AFTER triggers cannot be defined on views.


StackOverflow to the rescue: osea tengo razon y si se cancela el insert