Loken correctly predicted what would happen to him on Isstvan III pg 83 Horus Rising. This was a foretelling as i see it.
"Then, briefly , he imagined another death. Alone, far away from his comrades and his Legion, dying from cruel wounds on some nameless rock, his passing as memorable as smoke"
I think that was Loken waxing eloquent about the possibility of an ignominious death, not a psychic premonition.
As stated above: Loken. Was. Not. A. Psyker.
They test you for that stuff.