@Freyrs_storiesFor just a random comment, I would say I strongly agree that no magic can work on a person unless that person is alerted to it.
But yes, a quietly chanted spell can be sent by clapping ones hands, for example. Even if the person won't see the caster, even if they misinterpret what sound did they hear, if their flow is disturbed the spell can stick, easier still if the target may consider use of magic as a possibility for the source of their confusion.
The spell can get strong reinforcement and/or considerable power up (up to several magnitudes if measurable) if the receiver associate said disturbance with God's action, ideally from a God they follow. For example, if a Thunder follower may happen to counter-rationally attribute said hand clap without source, as they may believe, to a distant thunderstorm, and if the caster's intent wasn't crystal clear, the resulting consequences may be unexpectedly severe. If they mention that in conversation with others right then, an individually targeted spell may even inadvertently reapply to the entire group that heard both that clap and the attribution.
But if they don't get this WTF moment, because they don't hear it at all or disregard and carry on ignoring it completely the spell may fail.
Direct verbal commands in person or voice communication can be crafted as Loaded Words that while sounding almost mundane have special and specific meaning to the caster of the spell. Again, reaction from the target is needed, ideally affirmative, or consenting, no matter they have no idea to what exactly they're agreeing to, but indifferent confusion may be enough. A confident refusal however may fail the spell, with possible consequences for the caster through mirroring, expense, or otherwise, generally depending from the spell type, magic methodology, deities called for, and other factors.
Written magic I would consider a subtype of object magic, and it requires the target to see the Charged Object and ideally associate with themselves. Such as, for example, a hieroglyph sticker found in personal belongings or on one's persona or even body. Voodoo needle doll must be seen by the target and recognized as representing them, or at very least a third person should see it, make the recognition and then tell the target about it in enough detail (I don't care most literature may disregard this, admittedly inconvenient little detail, that's how I consider magic work, consistent with personal experience both casting and as a target).
In object magic the object should be recognized as unusual or out place, and manipulation of the object should at least be considered as possibility.
Yes, ignorance may sometimes be a great shield, but it is weak, passive and easy to manipulate.
