The current 'protected' message is "Bob tries to cast a spell on you, but you are protected." Not exactly helpful, you don't know what spell Bob tried to cast and you don't know why it didn't land. Would it be possible, maybe as an option, to get a more detailed message ? e.g. "Bob tries to cast <spellname> on you, but you are protected by <reason>.".
I think that message is mainly from a player trying to cast a Detrimental Spell on you. I'm not sure if you get it for other reasons or not though.