Trap still seems to be placed on whoever was chosen after Necromancer triggers trap with their ghoul.
In my case, it was placed on the mayor.
Example
N5 necro used ghoul to attack mayor, the message I received was, "Your trap attacked someone!"
N6 my trap logo and the ability to dismantle said trap was still present, so I just left the trap up.
Day 7- Mayor is dead to necro ghoul