OP again, I did manage to trigger the chasers event, though whenever I turned on the TV, the envelope disappeared. When the chasers finally popped up, the bird was on top of the envelope. I also made a new game and checked it and there was no envelope, however I noticed something.
Whenever I find the envelope (my regular save), the door to the Dream Apartments is between Geometry World and the Library. But on this new game (and I'm pretty sure on the beginning of my regular save as well), the Dream Apartments are between Toy World and Heart World.
I think that might make sense if we go with the theory of two different versions of the room, but I'm starting to think you might be right about my copy being glitched...