I don't always agree with @Oofta but I don't think I've ever seen him be dishonest.The funny thing is that they are dishonest.
Stealing part of the description. HAhaa
Yes, you took psychic damage.
It's all you know.
haha
Subtle Dominate Person doesn't have noticeable effect.
More relevantly, the person being dominated knows they're being dominated. The people around the person being dominated knows the person is acting strangely. So, even though they didn't notice that the caster cast the spell, there are effects they can notice.