Re: [THE CURRENT OPTIONS]
I think that their touch is so powerful that they'd trigger it before they saw it. In my experience -- particularly with Mirror -- delicacy is not on their minds when they probe, and any outside contact with either the trigger or the memories it protects will set it off.
And even if that's not the case, that's why it can be triggered voluntarily; it only takes a thought, and as soon as they're aware they're in danger of being probed, they're safe.