Yes, but it did originate in Meredith's room? It became watered down later. There was no water in the murder room, there was water in the bathroom, after all. So Raffaele had to step into a lot of blood and track it down to the bathroom, right?
Maybe I was too fast with the inference from your words. Bathmat print is barefoot = barefoot during the attack. Residual luminol prints left during cleaning are also bare feet. You don't agree?
But there must have been at some point, and it was cleaned up, leaving just 3 prints. Or were they sweeping their own prints while walking?
If it was not a foot, it would seem Amanda touched the floor with some other body part that had Meredith's blood on it, leaving her own and Meredith's DNA. Do I make sense?
I know we don't have all answers, I assure you. Don't worry about it. I'm trying to connect the dots and fill in the gaps together with you, to arrive at a scenario of what happened.