In GameMaker Studio 2, retrieve non-persistent object from another room

Question

I have a game which consists of 2 rooms - upper floor and lower floor. I want to create a path for an object on the lower floor, while the displayed room is the upper floor. The object that walks the path is persistent, but it will only be drawn if he's in the correct room - so that's not a problem. The problem is retrieving any collision objects which reside in the lower floor. They are non-persistent, so they don't "exist" while I'm in the upper floor. The only way I can think of doing this, is to make all the collision objects persistent, and simply check one by one which floor they are on, before using them. But that's not a great plan in my opinion. Is there any better way to get them? Thanks!