I'm quite certain the bed and bedding was still there and visible in a photo made public. Let me see if I can find it.
I agree that people were speculating all sorts of reasons why both girls were in the same bed, some reasonable and some offensive, but AFAIK there was nothing conclusive.
My personal opinion is that K went into M's room for some reason relating to the calls they were trying to make to K's ex. Though it also makes sense to me that they were already together in the same room talking prior to those calls, and that had the murders not happened, K would have returned to her own room to sleep. Or at least intended to -- if they were intoxicated as speculated, she could easily have fallen alseep before she meant to, while still in M's room/bed.
MOO for now
ETA: found the photo. If you zoom in, you can see a bed with bedding, and what looks like stacked cardboard boxes, though I suppose that could actually be furniture. The bed is the key thing though.
Photo is cropped by me from this article:
Idaho murders: Inside the off-campus house where 4 students were killed