OK, I know the rule is:
A save against a spell with no obvious physical effects feels like a hostile force or a tingle, but the exact nature of the attack is unknown. If a creature saves against your targeted spell you sense that the spell has failed.
However, that rule is specific. It is a save against a spell.
What happens when you successfully fend off a vampire's dominate, or a basidirond's spores?
If the player saves do they even know they happened, or are happening?
Dominate (Su): A vampire can crush
a humanoid opponent’s will as a
standard action. Anyone the
vampire targets must succeed on a Will save or fall instantly
under the vampire’s inf luence, as though by a dominate
person spell (caster level 12th).
Hallucination Cloud (Ex) As a standard action once per
minute, a basidirond can release a cloud of INVISIBLE
spores in a 20-foot radius. All creatures within the area
must succeed on a DC 16 Fortitude save or be affected by
powerful hallucinations as long as they remain in the cloud
plus 1d4 rounds after leaving the area.
I would prefer a solid written rule citing, or game creator judgement, but am open to debate and comments as well.
