Question about Vestige: Read Thoughts ability

[Stalker0]

I'm playing a binder with a vestige that allows me to read thoughts at will.

Its similiar to detect thoughts, but a little faster, and targets one creature.

Now its a supernatural ability, meaning there are NO components. I don't even have to look at the guy. However, it is a targeted effect, with a save.

If the target passes his save, does he know something was cast on him? What if he fails?

 

[Maleketh]

From the SRD:

A creature that successfully saves against a spell that has no obvious physical effects feels a hostile force or a tingle, but cannot deduce the exact nature of the attack.

If your target makes his save, he knows that someone was trying to do something to him, just not what. Admittedly, your binder's not using a spell, but I'd say it's close enough to have the same result.

I can't find a quote anywhere, but I don't believe the target is aware if he fails his save.