 And who knows why it was omitted, but it should not be omitted. We could say it's a valid Mass for sure, but it was not licit for the priest. If he intentionally omitted that, it wouldn't be licit. That would be a sin for him, but not for you. It wouldn't affect the spiritual fruitfulness for you or anyone there at that Mass. But yes, the short answer is yes, that would still be a valid Mass.