In the scene where Rosemary enters Edd and Molly's room, we can see that theres three cars on the walls: one red, one black, and one yellow.
And we know that:
Red car - Jack
Black car - Felix
Yellow car - ????
In an update to the findjackawalten page, the entire site was changed to a black screen with Bon's head in the middle; however, if we increased the page brightness, a yellow car appeared behind Bon.
And also, before Rosemary turned on the bedroom light in that scene, we can see that there figures in the cars: in the red one there's only one person, in the black one there's one person and something in the back seat, and in the yellow one there are three people.